`ZSTD_selectBlockCompressor` already delegated scalar strategy/index
calculation to the Rust parameter module, but C still owned table selection
and dictionary-mode offsets. Keep the configuration-dependent C function-
pointer tables and NULL entries for excluded compressors as private leaves,
and pass those tables through a narrow ABI state so Rust owns row versus
ordinary selection, dictionary-mode indexing, and selected callback
publication. The legacy C selector signature remains intact for the LDM
caller.
Test Plan:
- `rustfmt --edition 2021 --check rust/src/zstd_compress.rs` -- passed.
- `git diff --check` and `git diff --cached --check` -- passed.
- Heavy cargo/make/test/fuzzer verification not run per the enforced 40 GiB
serial verification limit.