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`.

0 files changed, 0 insertions, 0 deletions