This CL adds a new diffing implementation based on Myers algorithm
to live editing. We straight-up implement the algorithm presented in
"Myers, E.W. An O(ND) difference algorithm and its variations (1986)"
particularly the "Linear space refinement" presented in section 4b.

Note that the CL does not enable the new algorithm straight-away.
We'll land a separate CL for easier revertability.

Myers algorithm is a great improvement over the current dynamic
programming approach. Local benchmarking with a 130kB script
has shown drastic improvements both for time and space:

    Live editing script (Old line count 10236 vs New 10240)
    Dynamic Programming: 65701.931 ms
    Myers:               11.735 ms

Bug: chromium:1205288
Change-Id: I136f176f4a0d3c9a5dcd7a157c72c49c475bea19
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3804860Reviewed-by: Kim-Anh Tran <kimanh@chromium.org>
Commit-Queue: Simon Zünd <szuend@chromium.org>
Cr-Commit-Position: refs/heads/main@{#82243}