Within the inspector we should be consistent about passing the script ID
always as integer, and only convert to String16 when actually needed.
That (a) saves memory (and some runtime overhead) when stashing away
call frames, for example in case of async stack traces, and (b) reduces
confusion which representation to chose.

Bug: chromium:1162229
Change-Id: I9591931da0a307779372f36aba6e155ec22bbe3d
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2876856
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Commit-Queue: Yang Guo <yangguo@chromium.org>
Auto-Submit: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74410}