This is only used by ElementsKindToString(!).

Implement ElementsKindToString with a big 'ol switch. The compiler
will give us an error if we forget an ElementsKind.

Bug: v8:9183
Change-Id: I1ed73ecac33aa7318a97f31794473d9afa16961c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1624802
Commit-Queue: Peter Marshall <petermarshall@chromium.org>
Reviewed-by: Simon Zünd <szuend@chromium.org>
Cr-Commit-Position: refs/heads/master@{#61773}