Compiler benchmark harness (Rust + moc phase timings)

[christoph-dfinity]

Summary

Adds a Motoko compiler benchmark harness and per-phase timing in moc.

moc

• New --emit-compiler-timings <file> writes JSON phase durations on successful runs.
• New compiler_timing library; pipeline phases wrapped for measurement.

motoko-compiler-bench (Rust)

• Runs a TOML corpus (compiler-bench/corpus.toml): check and compile, wall time + parsed compiler timings.
• Prefers bin/moc from the repo when present (RTS env).
• Nix: compiler-bench package and dev shell.

Corpus

• Sample entries from test/perf, test/bench, and compiler-bench/fixtures/.

Made with Cursor

[github-actions]

Comparing from f816e6a to 10b9dd4:
The produced WebAssembly code seems to be completely unchanged.
In terms of gas, no changes are observed in 5 tests.
In terms of size, no changes are observed in 5 tests.