Revert of de-proc sk_float_rsqrt (patchset #3 id:40001 of https://codereview.chromium...

Revert of de-proc sk_float_rsqrt (patchset #3 id:40001 of https://codereview.chromium.org/1616013003/ )

Reason for revert:
This is somehow blocking the Google3 roll in ways neither Ben nor I understand.  Precautionary revert... will try again Monday.

Original issue's description:
> de-proc sk_float_rsqrt
>
> This is the first of many little baby steps to have us stop runtime-detecting NEON.
>
> BUG=skia:
> GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1616013003
> CQ_EXTRA_TRYBOTS=client.skia:Test-Ubuntu-GCC-GCE-CPU-AVX2-x86_64-Release-SKNX_NO_SIMD-Trybot
>
> Committed: https://skia.googlesource.com/skia/+/efcc125acd2d71eb077caf6db65fdd6b9eb1dc0d

TBR=reed@google.com,mtklein@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=skia:

Review URL: https://codereview.chromium.org/1629503002