IF: Bring back is_needed to avoid adding redundant QCs to blocks; enforce sensible finalizer policy in setfinalizers host function

[linh2931]

• If the QC claim in the to-be-assembled block is the same (same block number and strong/weak status) as the QC claim in the previous block, then the QC should not be included in the block extension. is_needed was removed by IF: Simplify code path when validating a received block. #2111 due to test failure. There was actually a bug in the original use of is_needed. It should have been used against parent block. This PR brings back is_needed and fixes the bug.

• If the sum of weights is less than threshold, the quorum will never be met. This PR asserts that the sum of the weights is greater than or equal to the threshold within the setfinalizers host function,

Resolved #2136

[heifner]

Seems we need AntelopeIO/reference-contracts#41

/__w/leap/leap/reference-contracts/tests/main.cpp(19): fatal error: in "eosio_bios_if_tests/set_1_finalizer": Caught Unexpected Exception
3070002 wasm_execution_error: Runtime Error Processing WASM
Finalizer policy threshold (4) cannot be met by finalizer weights (3)
    {"t":4,"w":3}

Before libtester tests will pass.

[heifner]

This does seem to fix the test failures I was seeing, here is a run of #2124 with this PR merged into it: https://github.com/AntelopeIO/leap/actions/runs/7649477360

[ericpassmore]

Note:start
group: IF
category: INTERNALS
summary: Avoid adding redundant QCs to blocks, by bringing back is_needed
Note: end