modules/ztd: surface metrics for zstd_dec

Spitting this from https://github.com/google/xls/pull/1857, as it's likely to require to be implemented separelty.

It would be nice to surface metrics for the `//xls/modules/zstd:zstd_dec_dslx` block:
- area estimate: post-synthesis, post-pnr
- algorithm throughput estimate: through block IR (and maybe verilog?) simulation across a representative corpus of zstd frames.
- algorithm delay independent of the size or type of the ztd frame.

Ideally those would be surfaced in the summary of workflow runs of PRs affecting the `modules/zstd`.