Restore --with-tests and --with-doc when OPAM 2.1 is available

[na4zagin3]

I temporarily disabled --with-tests and --with-doc flags because of cyclic dependency:

Error:  No solution for snapshot-develop: The actions to process have cyclic dependencies:
          - ∗ tyxml.4.4.0 → ∗ odoc.1.5.2 → ∗ dune-configurator.2.8.1 → ∗ graphics.5.1.0 → ∗ ocamlfind.1.8.1 → ∗ topkg.1.0.3 → ∗ uutf.1.0.2 → ∗ tyxml.4.4.0
          - ∗ alcotest.1.2.3 → ∗ tyxml.4.4.0 → ∗ odoc.1.5.2 → ∗ dune-configurator.2.8.1 → ∗ graphics.5.1.0 → ∗ ocamlfind.1.8.1 → ∗ topkg.1.0.3 → ∗ uutf.1.0.2 → ∗ alcotest.1.2.3
          - ∗ alcotest.1.2.3 → ∗ tyxml.4.4.0 → ∗ odoc.1.5.2 → ∗ dune-configurator.2.8.1 → ∗ graphics.5.1.0 → ∗ ocamlfind.1.8.1 → ∗ topkg.1.0.3 → ∗ uuidm.0.9.7 → ∗ alcotest.1.2.3
          - ∗ alcotest.1.2.3 → ∗ tyxml.4.4.0 → ∗ odoc.1.5.2 → ∗ dune-configurator.2.8.1 → ∗ graphics.5.1.0 → ∗ ocamlfind.1.8.1 → ∗ fmt.0.8.9 → ∗ alcotest.1.2.3
          - ∗ tyxml.4.4.0 → ∗ odoc.1.5.2 → ∗ dune-configurator.2.8.1 → ∗ graphics.5.1.0 → ∗ ocamlfind.1.8.1 → ∗ base-bytes.base → ∗ ounit2.2.2.4 → ∗ ounit.2.2.4 → ∗ re.1.9.0 → ∗ tyxml.4.4.0
          - ∗ alcotest.1.2.3 → ∗ tyxml.4.4.0 → ∗ odoc.1.5.2 → ∗ dune-configurator.2.8.1 → ∗ graphics.5.1.0 → ∗ ocamlfind.1.8.1 → ∗ base-bytes.base → ∗ ounit2.2.2.4 → ∗ ounit.2.2.4 → ∗ re.1.9.0 → ∗ alcotest.1.2.3
          - ∗ odoc.1.5.2 → ∗ dune-configurator.2.8.1 → ∗ graphics.5.1.0 → ∗ ocamlfind.1.8.1 → ∗ base-bytes.base → ∗ ounit2.2.2.4 → ∗ bisect_ppx.2.5.0 → ∗ odoc.1.5.2
          - ∗ odoc.1.5.2 → ∗ dune-configurator.2.8.1 → ∗ graphics.5.1.0 → ∗ ocamlfind.1.8.1 → ∗ astring.0.8.5 → ∗ odoc.1.5.2
          - ∗ odoc.1.5.2 → ∗ dune-configurator.2.8.1 → ∗ graphics.5.1.0 → ∗ ocamlfind.1.8.1 → ∗ astring.0.8.5 → ∗ fpath.0.7.3 → ∗ odoc.1.5.2
          - ∗ alcotest.1.2.3 → ∗ tyxml.4.4.0 → ∗ odoc.1.5.2 → ∗ dune-configurator.2.8.1 → ∗ graphics.5.1.0 → ∗ ocamlfind.1.8.1 → ∗ astring.0.8.5 → ∗ alcotest.1.2.3
          - ∗ ppx_jane.v0.14.0 → ∗ cinaps.v0.15.0 → ∗ ppxlib.0.15.0 → ∗ ppx_variants_conv.v0.14.1 → ∗ ppx_jane.v0.14.0
          - ∗ ppx_jane.v0.14.0 → ∗ cinaps.v0.15.0 → ∗ ppxlib.0.15.0 → ∗ ppx_typerep_conv.v0.14.1 → ∗ ppx_jane.v0.14.0
          - ∗ ppx_jane.v0.14.0 → ∗ cinaps.v0.15.0 → ∗ ppxlib.0.15.0 → ∗ ppx_stable.v0.14.1 → ∗ ppx_jane.v0.14.0
          - ∗ ppx_jane.v0.14.0 → ∗ cinaps.v0.15.0 → ∗ ppxlib.0.15.0 → ∗ ppx_pipebang.v0.14.0 → ∗ ppx_jane.v0.14.0
          - ∗ ppx_jane.v0.14.0 → ∗ cinaps.v0.15.0 → ∗ ppxlib.0.15.0 → ∗ ppx_optional.v0.14.0 → ∗ ppx_jane.v0.14.0
          - ∗ ppx_jane.v0.14.0 → ∗ cinaps.v0.15.0 → ∗ ppxlib.0.15.0 → ∗ ppx_optcomp.v0.14.0 → ∗ ppx_jane.v0.14.0
          - ∗ ppx_jane.v0.14.0 → ∗ cinaps.v0.15.0 → ∗ ppxlib.0.15.0 → ∗ ppx_let.v0.14.0 → ∗ ppx_jane.v0.14.0
          - ∗ base_quickcheck.v0.14.0 → ∗ ppx_jane.v0.14.0 → ∗ cinaps.v0.15.0 → ∗ ppxlib.0.15.0 → ∗ ppx_let.v0.14.0 → ∗ base_quickcheck.v0.14.0
          - ∗ ppx_jane.v0.14.0 → ∗ cinaps.v0.15.0 → ∗ ppxlib.0.15.0 → ∗ ppx_jane.v0.14.0
          - ∗ ppx_jane.v0.14.0 → ∗ cinaps.v0.15.0 → ∗ ppxlib.0.15.0 → ∗ ppx_here.v0.14.0 → ∗ ppx_sexp_value.v0.14.0 → ∗ ppx_jane.v0.14.0
          - ∗ base_quickcheck.v0.14.0 → ∗ ppx_jane.v0.14.0 → ∗ cinaps.v0.15.0 → ∗ ppxlib.0.15.0 → ∗ ppx_here.v0.14.0 → ∗ ppx_sexp_value.v0.14.0 → ∗ base_quickcheck.v0.14.0
          - ∗ ppx_jane.v0.14.0 → ∗ cinaps.v0.15.0 → ∗ ppxlib.0.15.0 → ∗ ppx_here.v0.14.0 → ∗ ppx_sexp_message.v0.14.0 → ∗ ppx_jane.v0.14.0
          - ∗ base_quickcheck.v0.14.0 → ∗ ppx_jane.v0.14.0 → ∗ cinaps.v0.15.0 → ∗ ppxlib.0.15.0 → ∗ ppx_here.v0.14.0 → ∗ ppx_sexp_message.v0.14.0 → ∗ base_quickcheck.v0.14.0
          - ∗ ppx_jane.v0.14.0 → ∗ cinaps.v0.15.0 → ∗ ppxlib.0.15.0 → ∗ ppx_here.v0.14.0 → ∗ ppx_jane.v0.14.0
          - ∗ ppx_jane.v0.14.0 → ∗ cinaps.v0.15.0 → ∗ ppxlib.0.15.0 → ∗ ppx_fixed_literal.v0.14.0 → ∗ ppx_jane.v0.14.0
          - ∗ ppx_jane.v0.14.0 → ∗ cinaps.v0.15.0 → ∗ ppxlib.0.15.0 → ∗ ppx_fields_conv.v0.14.1 → ∗ ppx_jane.v0.14.0
          - ∗ base_quickcheck.v0.14.0 → ∗ ppx_jane.v0.14.0 → ∗ cinaps.v0.15.0 → ∗ ppxlib.0.15.0 → ∗ ppx_fields_conv.v0.14.1 → ∗ base_quickcheck.v0.14.0
          - ∗ ppx_jane.v0.14.0 → ∗ cinaps.v0.15.0 → ∗ ppxlib.0.15.0 → ∗ ppx_custom_printf.v0.14.0 → ∗ ppx_jane.v0.14.0
          - ∗ ppx_jane.v0.14.0 → ∗ cinaps.v0.15.0 → ∗ ppxlib.0.15.0 → ∗ ppx_bin_prot.v0.14.0 → ∗ ppx_jane.v0.14.0
          - ∗ ppx_jane.v0.14.0 → ∗ cinaps.v0.15.0 → ∗ ppxlib.0.15.0 → ∗ ppx_base.v0.14.0 → ∗ ppx_string.v0.14.1 → ∗ ppx_jane.v0.14.0
          - ∗ ppx_jane.v0.14.0 → ∗ cinaps.v0.15.0 → ∗ ppxlib.0.15.0 → ∗ ppx_base.v0.14.0 → ∗ ppx_jane.v0.14.0
          - ∗ base_quickcheck.v0.14.0 → ∗ ppx_jane.v0.14.0 → ∗ cinaps.v0.15.0 → ∗ ppxlib.0.15.0 → ∗ ppx_base.v0.14.0 → ∗ base_quickcheck.v0.14.0
          - ∗ ppx_jane.v0.14.0 → ∗ cinaps.v0.15.0 → ∗ ppxlib.0.15.0 → ∗ ppx_assert.v0.14.0 → ∗ ppx_jane.v0.14.0
          - ∗ ppx_jane.v0.14.0 → ∗ cinaps.v0.15.0 → ∗ ppxlib.0.15.0 → ∗ ppx_assert.v0.14.0 → ∗ jst-config.v0.14.0 → ∗ time_now.v0.14.0 → ∗ ppx_module_timer.v0.14.0 → ∗ ppx_jane.v0.14.0
          - ∗ ppx_jane.v0.14.0 → ∗ cinaps.v0.15.0 → ∗ ppxlib.0.15.0 → ∗ ppx_assert.v0.14.0 → ∗ jst-config.v0.14.0 → ∗ time_now.v0.14.0 → ∗ ppx_inline_test.v0.14.1 → ∗ ppx_jane.v0.14.0
          - ∗ ppx_jane.v0.14.0 → ∗ cinaps.v0.15.0 → ∗ ppxlib.0.15.0 → ∗ ppx_assert.v0.14.0 → ∗ jst-config.v0.14.0 → ∗ time_now.v0.14.0 → ∗ ppx_inline_test.v0.14.1 → ∗ ppx_expect.v0.14.0 → ∗ ppx_jane.v0.14.0
          - ∗ base_quickcheck.v0.14.0 → ∗ ppx_jane.v0.14.0 → ∗ cinaps.v0.15.0 → ∗ ppxlib.0.15.0 → ∗ ppx_assert.v0.14.0 → ∗ jst-config.v0.14.0 → ∗ time_now.v0.14.0 → ∗ ppx_inline_test.v0.14.1 → ∗ ppx_bench.v0.14.1 → ∗ splittable_random.v0.14.0 → ∗ base_quickcheck.v0.14.0
          - ∗ ppx_jane.v0.14.0 → ∗ cinaps.v0.15.0 → ∗ ppxlib.0.15.0 → ∗ ppx_assert.v0.14.0 → ∗ jst-config.v0.14.0 → ∗ time_now.v0.14.0 → ∗ ppx_inline_test.v0.14.1 → ∗ ppx_bench.v0.14.1 → ∗ ppx_jane.v0.14.0
          - ∗ base_quickcheck.v0.14.0 → ∗ ppx_jane.v0.14.0 → ∗ cinaps.v0.15.0 → ∗ ppxlib.0.15.0 → ∗ base_quickcheck.v0.14.0


Command failed: opam list --readonly --with-test --with-doc --external  '--resolve=snapshot-develop' returned 20

According to mseri (ocaml/opam-repository#17724 (comment)), OPAM 2.1 can handle such situations. We need to restore the flags when it's available.