merge_pr_46964

Add a reftest for COLR-glyph compositing modes.

Differential Revision: https://phabricator.services.mozilla.com/D215475

bugzilla-url: https://bugzilla.mozilla.org/show_bug.cgi?id=1902253
gecko-commit: c2d7979b2ae323787d2c69b0ddac667c9b046cd1
gecko-reviewers: gfx-reviewers, lsalzman