Re-add `@private`, undocumented `.identifier` method that was only me… #7140

Job	Run time
benchmark	1m 34s
Test compatibility with Primer ViewComponents (main)	2m 12s
test (6.1, 3.0, capture_patch_enabled)	31s
test (6.1, 3.0, capture_patch_disabled)	53s
test (7.0, 3.1, capture_patch_enabled)	51s
test (7.0, 3.1, capture_patch_disabled)	46s
test (7.1, 3.2, capture_patch_enabled)	1m 8s
test (7.1, 3.2, capture_patch_disabled)	55s
test (7.2, 3.3, capture_patch_disabled)	57s
test (7.2, 3.3, capture_patch_enabled)	1m 4s
test (main, head, capture_patch_disabled)	41s
test (main, head, capture_patch_enabled)	44s
coverage	12s
	12m 28s

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