[turbofan] Restructure typer's operator dispatch

Remove some duplication and make it easier to type a specific operation
with given input types.

Change-Id: I70d0424a1d1bd6330aa381568728d8313d5ad25d
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2078541
Auto-Submit: Georg Neis <neis@chromium.org>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Commit-Queue: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66522}