feat(cpp): part of low-level bindings, their tests, and e2e CI config (WIP)

[slbotbm]

Which issue does this PR close?

Works towards completion of #2763

Rationale

To be merged after #2785

What changed?

Adds low-level bindings + tests + e2e CI config

Local Execution

• Passed
• Pre-commit hooks ran

AI Usage

If AI tools were used, please answer:

1. Which tools? codex
2. Scope of usage? code generation
3. How did you verify the generated code works correctly? Planned what needs to be implemented, created spec, and then verified all code generated and tests run.
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 67.90%. Comparing base (4f1044d) to head (cdfba8e).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #2852      +/-   ##
============================================
+ Coverage     67.55%   67.90%   +0.34%     
  Complexity      739      739              
============================================
  Files          1049     1049              
  Lines         84169    84385     +216     
  Branches      60746    60974     +228     
============================================
+ Hits          56859    57298     +439     
+ Misses        24958    24713     -245     
- Partials       2352     2374      +22     

Flag	Coverage Δ
csharp	67.43% <ø> (-0.19%)	⬇️
go	6.33% <ø> (ø)
java	54.83% <ø> (ø)
node	92.26% <ø> (-0.07%)	⬇️
python	0.00% <ø> (ø)
rust	70.21% <ø> (+0.50%)	⬆️

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see 25 files with indirect coverage changes

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