Simple implementations of:

    * Load[Immutable]CurrentContextSlot
    * Arithmetic with Smi immediate (AddSmi etc.)
    * TestEqual[Strict]

Bug: v8:7700
Change-Id: I895b60631b6a99296709bdf24709b7325a0e76e4
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3578854
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Victor Gomes <victorgomes@chromium.org>
Auto-Submit: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/main@{#79881}