[clang] move -Wcast-function-type under -Wextra (#77178)

The -Wcast-fuction-type-strict has been moved under dignstic group
-Wextra.
Edited the test cases for -Wcast-fuction-type-strict and
-Wcast-fuction-type in Sema an SemaCXX.

Added a new test case which include a functionality that was already in
the -Wextra group, i.e -Wignored-qualifiers with
-Wcast-fuction-type-strict.

Fixes: #76872