[Infra] Upgrade Gradle plugin dependencies and modernize codebase

[rlazo]

• Bump Firebase Performance plugin to 2.0.2 and Kotlin Gradle plugin to 2.0.21.
• Replace deprecated jcenter() repository references with mavenCentral() in tests.
• Update internal Kotlin code to use uppercase() instead of toUpperCase().
• Refactor type safety for attributes and properties by adding : Any bounds.
• Update Android API references and testing configurations for compatibility.

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[rlazo]

/gemini review

[github-actions]

plugins test results

69 tests   69 ✅  1m 30s ⏱️
12 suites   0 💤
12 files     0 ❌

Results for commit 0bf6ed9.

♻️ This comment has been updated with latest results.

[gemini-code-assist]

Code Review

This pull request updates several build configurations and dependencies, including upgrading the Kotlin Gradle plugin to 2.0.21, replacing deprecated jcenter() repositories with mavenCentral(), and updating compileSdkVersion to 34 in tests. It also migrates deprecated .toUpperCase() calls to .uppercase() and refines generic type constraints in Gradle extension functions. Feedback is provided regarding a compilation error in BaseFirebaseLibraryPlugin.kt, where accessing 'it.path' on a ProjectDependency is invalid and should be reverted to 'it.dependencyProject.path'.