[clang] Reset FP options before template instantiation

AST nodes that may depend on FP options keep them as a difference
relative to the options outside the AST node. At the moment of
instantiation the FP options may be different from the default values,
defined by command-line option. In such case FP attributes would have
unexpected values. For example, the code:

    template <class C> void func_01(int last, C) {
      func_01(last, int());
    }
    void func_02() { func_01(0, 1); }
    #pragma STDC FENV_ACCESS ON

caused compiler crash, because template instantiation takes place at the
end of translation unit, where pragma STDC FENV_ACCESS is in effect. As
a result, code in the template instantiation would use constrained
intrinsics while the function does not have StrictFP attribute.

To solve this problem, FP attributes in Sema must be set to default
values, defined by command line options.

This change resolves https://github.com/llvm/llvm-project/issues/63542.

Differential Revision: https://reviews.llvm.org/D154359