Fix broken ReFrame tests

[bedroge]

• don't parametrize the eessi repo dir variable, as that won't work anyway if the versions/architectures can be parametrized as well (repo has to be fixed in that case)
• drop support for the pilot repo by removing the checks for latest and 2021.12
• remove the host symlinks that we no longer use from the host symlink test

[eessi-bot]

Instance eessi-bot-mc-aws is configured to build for:

• architectures: x86_64/generic, x86_64/intel/haswell, x86_64/intel/skylake_avx512, x86_64/amd/zen2, x86_64/amd/zen3, aarch64/generic, aarch64/neoverse_n1, aarch64/neoverse_v1
• repositories: eessi.io-2023.06-compat, eessi-hpc.org-2023.06-software, eessi-hpc.org-2023.06-compat, eessi.io-2023.06-software

[eessi-bot]

Instance eessi-bot-mc-azure is configured to build for:

• architectures: x86_64/amd/zen4
• repositories: eessi.io-2023.06-software, eessi-hpc.org-2023.06-compat, eessi-hpc.org-2023.06-software, eessi.io-2023.06-compat

[ocaisa]

LGTM