[FPEnv][LibCallsShrinkWrap] Correct strictfp tests.

Correct ShrinkWrap strictfp tests to follow the rules documented
in the LangRef:
https://llvm.org/docs/LangRef.html#constrained-floating-point-intrinsics

These tests needed the strictfp attribute added to function calls.

Since I was here anyway I removed the strictfp attribute from
constrained intrinsic calls. After D154991 the constrained intrinsics
have the strictfp attribute by default so they don't need it here,
but other functions do.

Test changes verified with D146845.