port 5e9ddf6c (r35453)

  original commit message:
  Reland of (https://codereview.chromium.org/1617503003)

  * 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=

Review URL: https://codereview.chromium.org/1894923002

Cr-Commit-Position: refs/heads/master@{#35560}