chore: automate NOTICE generation

[dbjorge]

Details

In mid-April, ClearlyDefined (the backend Component Governance uses to identify license information of components) added support for dependencies that come from maven.google.com. That means that we no longer have to manually update our NOTICE.html file to accurately attribute Google's dependencies; we can switch to automatically generating the NOTICE files like we do in our other repos.

This PR implements:

• Removing the manually managed NOTICE.html file
• Removing the PR build check that it matches the lockfile
• Adding a release build task to generate the NOTICE file automatically
• Moving the task to validate that it matches the lockfile to right after generation (as a safety check that the NOTICE generator is configured correctly)
• Updated error output from the validation task accordingly
• Adds a new check (to both release and PR builds) that the lockfile is up to date (this is more important to do continuously now, since its accuracy affects NOTICE generation accuracy)

Example release build with a NOTICE validation failure due to intentionally checking incorrect boxes in NOTICE config in component governance: #20210918.2

Example passing release build with generated NOTICE file: #20210918.4

Motivation

Automates a confusing manual process

Context

n/a

Pull request checklist

• [n/a] Addresses an existing issue: #0000
• [n/a] Added/updated relevant unit test(s)
• Ran ./gradlew fastpass from AccessibilityInsightsForAndroidService
• PR title AND final merge commit title both start with a semantic tag (fix:, chore:, feat(feature-name):, refactor:).

[DaveTryon]

Great stuff! Thanks for adding this