[Inline] Enable constant folding for fpbuiltin sqrt

[bader]

Constant folding should meet any accuracy requirements enforceby the
fpbuiltin intrinsic as it provides correctly-rounded implementation.

[bader]

@intel/dpcpp-devops-reviewers, I see a new check. It fails on:

Failed Tests (1):
  SYCL :: MemorySanitizer/track-origins/check_host_usm.cpp

Is this the same issue as reported in #19585 or something new?

[maarquitos14]

LGTM, just a coding style nit.

[jcranmer-intel]

There's probably a few more places that fpbuiltin.sqrt can be considered equivalent to for optimizations, but these are the most important (and the only ones involved in constant folding, fwiw).