Revert of [Atomics] code stubs for atomic operations (patchset #28 id:530001 of https://codereview.chromium.org/1617503003/ )

Reason for revert:
[Sheriff] Roll was reverted. Please fix unused methods, see:
https://codereview.chromium.org/1884913002/

https://build.chromium.org/p/tryserver.chromium.win/builders/win_clang/builds/5585/steps/compile%20%28with%20patch%29/logs/stdio

Original issue's description:
> [Atomics] code stubs for atomic operations
>
> * New atomic code stubs for x64, ia32, arm, arm64
> * Add convenience functions JumpIfNotValidSmiValue, JumpIfUintNotValidSmiValue
>   to macro-assembler-ia32 (API based on x64 macro assembler)
> * Remove runtime implementation of Atomics.load, the code stub should always be
>   called instead
> * Add new test to mjsunit atomics test; check that Smi values of different
>   sizes are supported when possible, else fall back to HeapNumbers
>
> These changes were needed to add another codestub:
> * Bump kStubMajorKeyBits from 7 to 8
> * Reduce ScriptContextFieldStub::kSlotIndexBits from 13 to 12
>
> BUG=v8:4614
> LOG=y
>
> Committed: https://crrev.com/10b5febe11b318cfef130abae343183ac862e60d
> Cr-Commit-Position: refs/heads/master@{#35427}

TBR=jarin@chromium.org,bmeurer@chromium.org,rodolph.perfetta@gmail.com,binji@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=v8:4614

Review URL: https://codereview.chromium.org/1884883003

Cr-Commit-Position: refs/heads/master@{#35443}