[google_apis] Allow overriding main API key via a feature.

This CLs adds the capability to override the API key via a feature
parameter. This takes precedence over the baked-in value of the APIKey
(including the value in the plist file on Apple platforms).

Note: This CL also removes the google_apis/google_api_keys.cc and
instead simply includes google_apis/google_api_keys-inc.cc in the
source files in google_apis/BUILD. This ensures that the file is
properly tracked by the build system and appears in IDEs (e.g. Xcode)
and thus can be used during bebugging.

Bug: 333064918

Change-Id: Id146d73ca51bba49f8d7680d80cb2c13cc005225
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5424132
Reviewed-by: Alex Ilin <alexilin@chromium.org>
Commit-Queue: Mihai Sardarescu <msarda@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1291846}
NOKEYCHECK=True
GitOrigin-RevId: 165ac7877b6671923f979194ce366e818e1cc100
7 files changed