Don't mark lambda non-dependent if nested in a generic lambda. (#149121)

Fixes #118187
Fixes #156579

An instantiated `LambdaExpr` can currently be marked as
`LDK_NeverDependent` if it's nested within a generic lambda. If that
`LambdaExpr` in fact depends on template parameters introduced by the
enclosing generic lambda, then its dependence will be misreported as
"never dependent" and spurious diagnostics can result.

The fix here proposed is a bit ugly, but the condition that it's being
bolted onto already seems like a bit of a hack, so this seems no worse
for wear.

Note that #89702 surfaced this change because it caused the inner lambda
expression to (correctly) be considered in a constant-evaluated context.
The affected check for whether to mark the inner lambda as
`LDK_NeverDependent` therefore started to apply, whereas it didn't
before.

**Tested**: `check-clang` and `check-cxx`.
3 files changed
tree: 11ab6855bfc08c95fe022ea3cd146a54dcc094a8
  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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