Reland "Add GN arg "enable_src_internal" and GN global "is_internal_chrome_branded""

This reverts commit 20ac2184802264975e3a591a85f1464f960490d5.

Reason for reland: Fixed failing tests (PS1->PS2)

Original change's description:
> Revert "Add GN arg "enable_src_internal" and GN global "is_internal_chrome_branded""
>
> This reverts commit 28bcf1e997b12cbb41217a2d17fcd6d3694261a9.
>
> Reason for revert: Likely caused test breakage on automotive builders
>
> Original change's description:
> > Add GN arg "enable_src_internal" and GN global "is_internal_chrome_branded"
> >
> > Rather than have to maintain a separate non-internal checkout, it's more
> > convenient to be able to just set a GN arg to disable the internal bits.
> >
> > This updates most spots that used "is_chrome_branded" as a proxy for
> > "checkout_src_internal".
> >
> > Bug: 452971335
> > Change-Id: Icf33c5afddce68f82e31d3f3cc521e9340a8207f
> > Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7080502
> > Reviewed-by: Peter Wen <wnwen@chromium.org>
> > Commit-Queue: Andrew Grieve <agrieve@chromium.org>
> > Owners-Override: Andrew Grieve <agrieve@chromium.org>
> > Cr-Commit-Position: refs/heads/main@{#1536021}
>
> Bug: 452971335
> Bug: 455713087
> No-Presubmit: true
> No-Tree-Checks: true
> No-Try: true
> Change-Id: I1eeefbbd6ec2af802fbdb0c3cde354953d27542a
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7090032
> Owners-Override: Shuhei Takahashi <nya@chromium.org>
> Commit-Queue: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
> Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
> Auto-Submit: Shuhei Takahashi <nya@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#1536448}

Bug: 452971335
Bug: 455713087
Change-Id: I337244821723d837feac78c07ede5e4ae7487cc0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7088714
Reviewed-by: Peter Wen <wnwen@chromium.org>
Commit-Queue: Andrew Grieve <agrieve@chromium.org>
Owners-Override: Andrew Grieve <agrieve@chromium.org>
Commit-Queue: Peter Wen <wnwen@chromium.org>
Auto-Submit: Andrew Grieve <agrieve@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1536741}
NOKEYCHECK=True
GitOrigin-RevId: 6fab1f642e80e5a0719630b643ddf05fb94dd998