Cache the set of active transfers in receive arbiter

[fknorr]

receive_arbiter tracks a transfer for every transfer id it learns through an inbound pilot, so long-running programs like wave_sim -T 10000 will fill the transfer map quickly. It's an unordered_map so lookups shouldn't suffer, but we iterate over it in poll_communicator, which has linear complexity (initially found by @psalz).

We only need to poll transfers for which we have already seen the receive_instruction. This PR avoids the linear growth by caching the set of active transfers in a vector, and iterating over that.

I've used the opportunity to refactor the code a bit and use std::erase_if in the many places we had erase-remove idiom before.

[github-actions]

Check-perf-impact results: (000e2892abb21ddd1ae413a5c86d7d95)

❓ No new benchmark data submitted. ❓
Please re-run the microbenchmarks and include the results if your commit could potentially affect performance.

[coveralls]

Pull Request Test Coverage Report for Build 12304599460

Details

• 41 of 42 (97.62%) changed or added relevant lines in 2 files are covered.
• 3 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.03%) to 94.984%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/receive_arbiter.cc	38	39	97.44%

Files with Coverage Reduction	New Missed Lines	%
src/receive_arbiter.cc	3	96.09%

Totals
Change from base Build 12236072360:	-0.03%
Covered Lines:	7090
Relevant Lines:	7202

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💛 - Coveralls