chore: rename c++ codecs and use portable C++ submodule

[nyurik]

• no code changes - just rename all C++ codecs to Cpp* without the Codec suffix.
• bump C++ dependency to the latest main - i think this is the reason the last release didn't handle portable C++ properly

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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[Copilot]

Pull request overview

Renames the Rust-side C++ codec wrapper types to the Cpp* naming scheme (dropping the *Codec suffix) and updates the vendored C++ submodule revision to improve portability.

Changes:

• Renamed C++ codec wrapper types throughout tests, benchmarks, fuzzers, and documentation to Cpp*.
• Updated cpp git submodule to a newer commit.
• Minor tooling tweak in justfile to use pushd/popd during formatting.

Reviewed changes

Copilot reviewed 12 out of 12 changed files in this pull request and generated 8 comments.

Show a summary per file

File	Description
tests/cpp_compat_tests.rs	Updates tests to use the renamed Cpp* codec types.
tests/benchmark_smoke.rs	Updates smoke tests to construct CppFastPFor128.
src/cpp/tests.rs	Updates macro-driven C++ codec tests to the new Cpp* names and refactors macro patterns.
src/cpp/codecs.rs	Renames exported wrapper types to Cpp* and updates internal tests/docs accordingly.
justfile	Uses pushd/popd instead of cd in the fmt recipe.
fuzz/fuzz_targets/rust_decompress_oracle.rs	Switches fuzz target to instantiate Cpp* codecs.
fuzz/fuzz_targets/rust_compress_oracle.rs	Switches fuzz target to instantiate Cpp* codecs.
fuzz/fuzz_targets/common.rs	Updates codec factory to return Cpp* codec instances.
cpp	Bumps the C++ submodule commit (portable C++ update).
benches/fastpfor_benchmark.rs	Updates benchmarks to use CppFastPFor128.
benches/bench_utils.rs	Updates helpers to accept CppFastPFor128.
README.md	Updates docs example to use CppSimdFastPFor128.

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