Add Bazel benchmark target and CodSpeed CI workflow (frankslin/OpenCC#31)

[frankslin]

• Add Bazel benchmark target and CodSpeed CI workflow

Performance.cpp path resolution now checks env vars before compile-time macros, and in Bazel builds uses Runfiles::Create(argv0) to locate configs, dictionaries, test data, and the opencc CLI binary via the .runfiles/ directory produced by bazel build. Jieba benchmarks are excluded (OPENCC_BENCHMARK_JIEBA_CONFIG_DIR undefined); text_json variants are skipped gracefully during global init when runfiles are not yet available.

Detailed Changes:

• Performance.cpp:
  • Add GetEnv() helper; add file-scope g_argv0/g_runfiles initialized in main() before benchmark execution.
  • All path functions follow: env var → Runfiles::Rlocation (BAZEL) → compile-time macro (CMake) → safe default.
  • Initialize() passes g_argv0 to SimpleConverter so its internal Runfiles::Create(argv0) resolves configs and dictionaries.
  • BuildBenchmarkConfigs() catches Exception& so text_json creation failures during global init are silently skipped.
• src/benchmark/BUILD.bazel: new cc_binary; deps include google-benchmark, opencc libs, and @bazel_tools//tools/cpp/runfiles; data covers configs, dictionaries, test data, and command_line binary.
• test/benchmark/BUILD.bazel: export zuozhuan.txt as benchmark_data.
• .github/workflows/codspeed.yml: single Ubuntu job; bazel build //src/benchmark:performance; run binary directly via runfiles with only OPENCC_BENCHMARK_TEMP_DIR set; uses CODSPEED_TOKEN_FRANKSLIN secret.

• Extend CodSpeed workflow trigger to opencc-wasm-develop branch

• Wire CodSpeed compat library and fix benchmark registration order

Switch the benchmark binary to @codspeed_google_benchmark_compat (simulation mode) so CodSpeed can identify individual benchmark boundaries; add the required --compilation_mode=dbg and --copt=-O2 flags to the CI workflow. Move RegisterBenchmarks() out of the anonymous namespace and call it in main() after Bazel runfiles are initialised, so text_json variants are no longer silently skipped in Bazel builds.

Detailed Changes:

• MODULE.bazel:
  • Add bazel_dep for codspeed_google_benchmark_compat 2.1.0 (dev_dependency).
• src/benchmark/BUILD.bazel:
  • Replace //deps/google-benchmark:benchmark with @codspeed_google_benchmark_compat//:benchmark.
• src/benchmark/Performance.cpp:
  • Remove kBenchmarksRegistered global; add DoRegisterBenchmarks() wrapper in opencc namespace.
  • Call opencc::DoRegisterBenchmarks() in main() after g_runfiles is initialised.
• .github/workflows/codspeed.yml:
  • Pass --@codspeed_google_benchmark_compat//:codspeed_mode=simulation, --compilation_mode=dbg, --copt=-O2 to bazel build.

• Fix CodSpeed benchmark naming and suppress DEBUG timing warning

Add Performance:: namespace prefix to all registered benchmark names so CodSpeed can identify their source file instead of falling back to unknown_file::. Update BenchmarkGroupName to strip the :: prefix before matching group labels. Add --copt=-DNDEBUG to the workflow build flags so NDEBUG is defined alongside --compilation_mode=dbg, eliminating Google Benchmark's spurious "Library was built as DEBUG" timing warning.

[BYVoid]

What does CodSpeed do

[frankslin]

What does CodSpeed do

CodSpeed helps detect performance regressions in code changes by running instrumented benchmarks in CI and comparing results over time.