[Fonts API] Allow using font-technologies for variable fonts

[aristath]

What?

Allows defining tech for font-families.
Fixes #41158, see comment on #41158 (comment) for details.

Why?

To allow using variable fonts files, while at the same time we keep forward-compatibility with the next-gen formats and font technologies.

[github-actions]

Flaky tests detected in 873ffbd.
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/4636521747
📝 Reported issues:

• [Flaky Test] doesn't throw a block error when clicking on a link #47747 in /test/e2e/specs/site-editor/template-part.spec.js
• [Flaky Test] prevent the removal of locked column block from the column count change UI #49534 in /test/e2e/specs/editor/blocks/columns.spec.js

[github-actions]

Warning: Type of PR label error

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• Labels found: [Feature] Typography.

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[hellofromtonya]

This PR is for the deprecated Fonts API. The API does not load into memory when the Font Library is active, which is by default. Thus I think this PR can be closed without merging.

The technical details of it might be something to consider, though the underlying issue was closed.