[Sema] Fix crash when evaluating nested call with value-dependent arg

Fix an edge case `ExprConstant.cpp`'s `EvaluateWithSubstitution` when called by `CheckEnableIf`

The assertion in `CallStackFrame::getTemporary`
could fail during evaluation of nested calls to a function
using `enable_if` when the second argument was a
value-dependent expression.

This caused a temporary to be created for the second
argument with a given version during the
evaluation of the inner call, but we bailed out
when evaluating the second argument of the
outer call due to the expression being value-dependent.
After bailing out, we tried to clean up the argument's value slot but it
caused an assertion to trigger in `getTemporary` as
a temporary for the second argument existed, but only for the inner call and not the outer call.

See the test case for a more complete description of the issue.

Reviewed By: ahatanak

Differential Revision: https://reviews.llvm.org/D139713