feat(ci): dependency-DAG-based test scoping for Rust CI

[krishvishal]

Which issue does this PR close?

Closes #3094

Summary

• Add scripts/ci/affected-crates.py that uses cargo metadata + git diff to compute affected crates via the workspace dependency DAG, then scopes cargo build and cargo nextest run to only those crates
• Fix two detection blind spots: core/iobuf and core/server-ng were not covered by any component in components.yml
• Split rust-simulator out of rust-cluster so simulator-only changes don't trigger Python/Node/Go/Java/C# SDK tests

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 72.69%. Comparing base (af92730) to head (43264cb).

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #3095      +/-   ##
============================================
- Coverage     72.73%   72.69%   -0.04%     
  Complexity      943      943              
============================================
  Files          1117     1117              
  Lines         96342    96342              
  Branches      73541    73557      +16     
============================================
- Hits          70070    70034      -36     
- Misses        23722    23737      +15     
- Partials       2550     2571      +21     

Components	Coverage Δ
Rust Core	73.45% <ø> (-0.04%)	⬇️
Java SDK	62.30% <ø> (ø)
C# SDK	69.10% <ø> (-0.33%)	⬇️
Python SDK	81.43% <ø> (ø)
Node SDK	91.44% <ø> (+0.12%)	⬆️
Go SDK	38.97% <ø> (ø)
see 23 files with indirect coverage changes

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