[clang-format] Add per-operator granularity for BreakBinaryOperations (#181051)

## Summary

Extend `BreakBinaryOperations` to accept a structured YAML configuration
with per-operator break rules and minimum chain length gating via
`PerOperator`.

- **Per-operator rules**: specify break style (`Never`, `OnePerLine`,
`RespectPrecedence`) for specific operator groups
- **Minimum chain length**: only trigger breaking when a chain has N or
more operators
- **Fully backward-compatible**: the simple scalar form
(`BreakBinaryOperations: OnePerLine`) behaves identically to the current
enum value

RFC discussion:
https://discourse.llvm.org/t/rfc-per-operator-granularity-for-breakbinaryoperations/89800

### New YAML syntax

```yaml
BreakBinaryOperations:
  Default: Never
  PerOperator:
    - Operators: ['&&', '||']
      Style: OnePerLine
      MinChainLength: 3
    - Operators: ['|']
      Style: OnePerLine
```

### Motivation

`BreakBinaryOperations` operates at the level of all binary operators
simultaneously. Enabling `OnePerLine` for `&&`/`||` condition chains
also forces it on `+`, `|`, and other operators, which may not be
desired. The only workaround today is `// clang-format off`.

## Test plan

- [x] All existing `BreakBinaryOperations` unit tests updated and
passing
- [x] New tests for per-operator rules (`&&`/`||` OnePerLine + default
Never)
- [x] New tests for multiple operator groups (`&&`/`||` + `|`)
- [x] New tests for `MinChainLength` gating (chain of 2 vs 3+)
- [x] Config parse tests for structured YAML form
- [x] RST documentation auto-generated via `dump_format_style.py`
- [x] Release notes updated
9 files changed
tree: fb694ae7af9d8924a20093b2d727b902b4a5976d
  1. .ci/
  2. .github/
  3. bolt/
  4. clang/
  5. clang-tools-extra/
  6. cmake/
  7. compiler-rt/
  8. cross-project-tests/
  9. flang/
  10. flang-rt/
  11. libc/
  12. libclc/
  13. libcxx/
  14. libcxxabi/
  15. libsycl/
  16. libunwind/
  17. lld/
  18. lldb/
  19. llvm/
  20. llvm-libgcc/
  21. mlir/
  22. offload/
  23. openmp/
  24. orc-rt/
  25. polly/
  26. runtimes/
  27. third-party/
  28. utils/
  29. .clang-format
  30. .clang-format-ignore
  31. .clang-tidy
  32. .git-blame-ignore-revs
  33. .gitattributes
  34. .gitignore
  35. .mailmap
  36. CODE_OF_CONDUCT.md
  37. CONTRIBUTING.md
  38. LICENSE.TXT
  39. pyproject.toml
  40. README.md
  41. SECURITY.md
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