chore(null): strict null checks for more injected/visualization files

[dbjorge]

Details

This PR continues from #6223 and fixes another few layers of injected/visualization files to be strict null check compatible. It substantially refactors accessibile-name-formatter and somewhat refactors landmark-formatter - I manually smoke tested those ad hoc tools to verify that they still worked after the changes

Motivation

#2869

Context

n/a

Pull request checklist

• Addresses an existing issue: Codebase should use strict null checks #2869
• Ran yarn null:autoadd
• Ran yarn fastpass
• Added/updated relevant unit test(s) (and ran yarn test)
• Verified code coverage for the changes made. Check coverage report at: <rootDir>/test-results/unit/coverage
• PR title AND final merge commit title both start with a semantic tag (fix:, chore:, feat(feature-name):, refactor:). See CONTRIBUTING.md.
• [n/a] (UI changes only) Added screenshots/GIFs to description above
• [n/a] (UI changes only) Verified usability with NVDA/JAWS

[peterdur]

Built, ran tests, visually verified accessible name behavior.
LGTM!

[lisli1]

LGTM