fix(react-native-cli): ensure kotlin files are updated

[yousif-bugsnag]

Goal

Builds on #2091 to ensure that the React Native CLI updates native Android files correctly in React Native 0.73 projects.

The previous PR updated the file lookup to find MainApplication.kt files as well as MainApplication.java, but the subsequent update still fails as it was still looking for java code snippets.

In addition, the CLI was still suggesting BAGP version 7.+ for RN 0.73, but should be suggesting 8.+

Design

• Added Kotlin code snippets and regexes for updating MainApplication.kt files
• getSuggestedBugsnagGradleVersion now attempts to suggests a version based on the detected React Native version when the AGP version is not found in the Gradle file (recent versions of React Native do not explicitly set the AGP version in the root build.gradle file)

Testing

Added unit test cases and tested manually on fresh RN 0.71, 0.72 and 0.73 projects

[github-actions]

@bugsnag/browser bundle size diff

	Minified	Minfied + Gzipped
Before	43.70 kB	13.40 kB
After	43.70 kB	13.40 kB
±	No change	No change

code coverage diff

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