Add sentencepiece@0.2.2

[BYVoid]

Adds SentencePiece v0.2.2, following up on #9552 (sentencepiece@0.2.1).

Same approach as 0.2.1, with the Bazel build definitions taken from the upstream PR google/sentencepiece#1280 (not yet merged), adapted for the 0.2.2 release tarball:

• overlay/BUILD.bazel + overlay/src/BUILD.bazel: root aliases, //src:sentencepiece (runtime), //src:sentencepiece_train (trainer), and the spm_{train,encode,decode,normalize,export_vocab} CLIs. The protobuf code is regenerated from src/*.proto at build time (matching the SPM_PROTOBUF_PROVIDER=package CMake configuration).
• patches/use_bcr_dependency_includes.patch: rewrites #include "third_party/absl/..." → "absl/...", "third_party/darts_clone/darts.h" → "darts.h", and "third_party/esaxx/esa.hxx" → "esa.hxx" so the sources resolve against the BCR modules (abseil-cpp, darts-clone@0.32h.bcr.1, esaxx@20250106.1.bcr.1) instead of the vendored copies.
• The release tarball is a Python sdist, so strip_prefix is sentencepiece-0.2.2/sentencepiece. It does not ship the data/ directory, so the upstream spm_test target is not included. Instead, the overlay adds a bcr_tests/ test module (bcr_test_module in presubmit) with an in-memory train → encode → decode roundtrip cc_test; presubmit also verifies all library and CLI targets on Linux/macOS/Windows with C++17 flags.

Differences from 0.2.1: 0.2.2 uses init.cc (renamed from error.cc), migrated to absl::Status/log (more abseil-cpp deps, no _USE_EXTERNAL_ABSL define needed), and its MODULE.bazel pins abseil-cpp 20260526.0 to match the GIT_TAG in CMakeLists.txt.

Locally verified: all targets build (Bazel 9.1.1), the bcr_tests roundtrip test passes, and bcr_validation.py --check sentencepiece@0.2.2 passes.

[bazel-io]

Hello BCR maintainers, modules (sentencepiece) have been updated in this PR.
Please review the changes. You can view a diff against the previous version in the "Generate module diff" check.

[bazel-io]

All modules in this PR have been approved by their maintainers. This PR will be merged if all presubmit checks pass.