feat(cpp): Add bazel building and testing infrastructure

[slbotbm]

Which issue does this PR close?

Closes #2762

Rationale

What changed?

Adds bazel build system + stub classes and their tests + ci scripts

Local Execution

• Passed
• Pre-commit hooks ran

AI Usage

If AI tools were used, please answer:

1. Which tools? codex
2. Scope of usage? build system implementation
3. How did you verify the generated code works correctly? checking on local environment
4. Can you explain every line of the code if asked? Yes

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 68.29%. Comparing base (b7818db) to head (0e8387f).

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #2785      +/-   ##
============================================
- Coverage     68.30%   68.29%   -0.02%     
  Complexity      656      656              
============================================
  Files           741      741              
  Lines         62210    62210              
  Branches      58623    58623              
============================================
- Hits          42495    42485      -10     
- Misses        17601    17611      +10     
  Partials       2114     2114              

Flag	Coverage Δ
java	52.19% <ø> (ø)
rust	69.35% <ø> (-0.02%)	⬇️

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see 6 files with indirect coverage changes

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