Move the pure LDM parameter-defaulting policy behind the original
ZSTD_ldm_adjustParameters() ABI symbol. Rust now receives the existing C
parameter structs directly, applies the same 30/8/8 build constants, and
keeps the ASAN-sensitive table-size projection in C.
Test Plan:
- `cc -fsyntax-only -Ilib -Ilib/common -Ilib/compress -Ilib/decompress -Ilib/dict -Ilib/legacy lib/compress/zstd_ldm.c` -- passed.
- `cargo +nightly fmt --manifest-path rust/Cargo.toml --all -- --check` -- passed.
- `git diff --check` and `git diff --cached --check` -- passed.
- Heavy verification intentionally deferred until the combined seam set is ready.