chore(null): null check fixes

[madalynrose]

Details

This PR fixes strict null checks for a few different files. These files were selected by running yarn null:find, added to tsconfig.strictNullChecks.json one-by-one, judged on whether their resolutions were straightforward enough to not require their own PR (removed if complex), and addressed.

I recommend going through this PR commit-by-commit, as each file from yarn null:find is scoped to a single commit.

• src/common/rule-based-view-model-provider.ts: allow various methods to return null
• src/background/stores/tab-store.ts: update TabStoreData to accept undefined values for url, title, and id, as that is what is returned from the chrome.tabs API
• accept undefined values for description, url, and guidance` for RuleResults, as returned by axe
• src/DetailsView/components/interactive-header.tsx: update InteractiveHeader to exclude items (an optional param) instead of passing null
• make originalResult optional and default to undefined, as it is optional in the data returned from axe

Motivation

#2869

Context

More PRs like this to follow, trying to keep PRs relatively small and well-chunked.

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

[pownkel]

LGTM