[clang] [Sema] Add lambda decltype((x)) semantics to blocks (#207355) (PR #207583)

[Bohdan Yehorov via cfe-commits]

BohdanYehorov wrote:

For lambda by reference in block `decltype((x))` returns a reference to a constant type, but for block in lambda by reference it returns a reference to a non-constant type. I tested `decltype((x))` result for a captured references in block: it returns a reference to a non-constant type.

https://github.com/llvm/llvm-project/pull/207583