chore: Resolve warnings in Gradle scripts

[mattcreaser]

• PR title and description conform to Pull Request guidelines.

Issue #, if available:

Description of changes:
Resolved a few warnings in our Gradle builds

• Using deprecated project.buildDir (should be project.layout.buildDirectory)
• Using unsupported build tools (build tools version is now set automatically by AGP)
• Specifying useless targetSdk in a library project (only app projects should set targetSdk)
• Using deprecated packagingOptions (renamed to packaging)
• Unable to resolve androidx.annotation:annotation:1.1.0 - I'm not sure why this happens since that artifact does exist, but upgrading to 1.9.1 appears to resolve 🤷‍♂️

This PR does not resolve compilation warnings, only warnings from the Gradle build itself.

How did you test these changes?

• Ran clean build, observed no more warnings

Documentation update required?

• No
• Yes (Please include a PR link for the documentation update)

General Checklist

• Added Unit Tests
• Added Integration Tests
• Security oriented best practices and standards are followed (e.g. using input sanitization, principle of least privilege, etc)

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.