[Webfonts] Use Core's _deprecated_argument() for deprecating data structures

[hellofromtonya]

Fixes #47123.

What?

Use Core's _deprecated_argument() instead of trigger_error() for deprecating data structures. This is similar to how deprecated functions in the API's BC layer uses Core's _deprecated_function().

Why?

To avoid filling server logs on production sites. _deprecated_argument() is Core's standard and will only display the deprecation when WP_Debug is on.

How?

See above.

Testing Instructions

With WP_Debug off:

1. Active TT3.
2. Active the Gutenberg plugin.
3. Install this testing plugin which uses Jetpack's Google Font Provider and deprecated functionality and data structures.
4. Run the site.
5. Open the server logs. > Notice there no deprecations.

Now turn on WP_Debug:
Repeat steps 1-5. Notice there are deprecations.

Testing Instructions for Keyboard

Screenshots or screencast

[aristath]

Code looks good, but the PR should be rebased since the file has been moved

[fullofcaffeine]

This tests well! 🐑

[hellofromtonya]

Rebased to trunk (for the API renaming) ✅

[github-actions]

Flaky tests detected in 19d0f57.
Some tests passed with failed attempts. The failures may not be related to this commit but are still reported for visibility. See the documentation for more information.

🔍 Workflow run URL: https://github.com/WordPress/gutenberg/actions/runs/3987197064
📝 Reported issues:

• [Flaky Test] results in two remaining blocks and positions the caret at the end of the second block #39805 in specs/editor/various/block-deletion.test.js

[hellofromtonya]

The failure on the "React Native E2E Tests (Android)" are unrelated to this PR. Restarting that CI Job for the third time. But it fails again, will ignore and merge this PR.