Compare the compiler's allocations with the base branch in CI
Timings on shared runners are too noisy to alert on, which is why the previous benchmark job was removed. The words the compiler allocates are the same in every run, so a new job measures them for the base branch and the pull request, fails when a benchmark allocates more than 1% more, and comments the comparison on the pull request.
The syntax benchmarks and make bench are removed; the comparison parses and formats their files with bsc, from tests/alloc_benchmarks/data.