Introduce auto-populated Search Engine icons.

This change is intended to replace the search_engine_choice assets
under //components/resources/.

This change introduces Search Engine assets populated automatically
by Copybara workflow in an effort to deprecate a best-effort, manual
Search Engine icon update process, needed by Search Engine Choice
dialog.

Newly introduced, offline Search Engine assets can be referenced by
the base_builtin_resource_id field.

The `base_builtin_resource_id` field is intentionally a string to
make assets available from webui. The relevant resources (currently
images, but soon also marketing snippets) can be constructed from
the `base_id` and an appropriate suffix.

Change-Id: I9dbad8ca8b05c2184f99743025f945610d01dffa
Bug: 409095783
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6470924
Reviewed-by: Ted Choc <tedchoc@chromium.org>
Commit-Queue: Tomasz Wiszkowski <ender@google.com>
Reviewed-by: Orin Jaworski <orinj@chromium.org>
Reviewed-by: Samuel Huang <huangs@chromium.org>
Reviewed-by: Nicolas Dossou-Gbété <dgn@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1456521}