[AST][RecoveryExpr] Make DeduceAutoType fail if the auto is deduced from recovery...

[AST][RecoveryExpr] Make DeduceAutoType fail if the auto is deduced from recovery exprs.

Summary:
With recovery-ast, we will get an undeduced `auto` return type for
"auto foo()->undef()" function declaration, the function decl still keeps
valid, it is dangerous, and breaks assumptions in clang, and leads crashes.

This patch invalidates these functions, if we deduce autos from the
return rexpression, which is similar to auto VarDecl.

Subscribers: cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D80221