[clang][AST] Propagate the contains-errors bit to DeclRefExpr from VarDecl's initializer.

Similar to the https://reviews.llvm.org/D86048 (it only sets the bit for C++
code), we propagate the contains-errors bit for C-code path.

Fixes https://github.com/llvm/llvm-project/issues/50236
Fixes https://github.com/llvm/llvm-project/issues/50243
Fixes https://github.com/llvm/llvm-project/issues/48636
Fixes https://github.com/llvm/llvm-project/issues/50320

Differential Revision: https://reviews.llvm.org/D154861