Install androidx.lint-gradle plugin to flag common Gradle problems

[scana]

Hi!

Unfortunately, still seeing some issues with Gradle Project Isolation when using Gradle 9.7 and Gradle Play Publisher 4.1.1.

I would like to attempt fixing them but noticed that the project could benefit from set of lint checks provided by Google that flag deprecations or project isolation violations.

This PR:

• installs androidx.lint-gradle (https://developer.android.com/jetpack/androidx/releases/lint#1.0.0)
• creates a new GHA workflow that runs lint checks and prints out a summary (I wouldn't make it mandatory until all issues are fixed) - this fails on purpose

Example problems flagged by lint checks:

.../gradle-play-publisher/play/plugin/src/main/kotlin/com/github/triplet/gradle/play/tasks/InstallInternalSharingArtifact.kt:192:
Error: Use Project.providers.environmentVariable instead of getenv [GradleConfigurationCacheBroadInputs from androidx.lint:lint-gradle]
                          System.getenv("ANDROID_SERIAL")
                                 ~~~~~~

.../gradle-play-publisher/play/plugin/src/main/kotlin/com/github/triplet/gradle/play/internal/Plugins.kt:56: 
Error: Use isolated.rootProject instead of getRootProject [GradleProjectIsolation from androidx.lint:lint-gradle]
    val project = if (extension.isolatedSingleProject.get()) this else rootProject
                                                                       ~~~~~~~~~~~

Those issues will also be highlighted in the IDE.

[SUPERCILEX]

Looks like you need to do this:

Fix the issues identified by lint, or create a baseline to see only new errors.
To create a baseline, run `gradlew updateLintBaseline` after adding the following to the module's build.gradle file:

lint {
baseline = file("lint-baseline.xml")
}

For more details, see https://developer.android.com/studio/write/lint#snapshot

[scana]

@SUPERCILEX ah right - I can just update the baseline 🤦

Shall we keep tests + lint under a single GHA job? (check task will run lint under the hood)

[SUPERCILEX]

Shall we keep tests + lint under a single GHA job? (check task will run lint under the hood)

Yeah, that seems nicer.

[scana]

@SUPERCILEX done! Although it seems like PromoteReleaseIntegrationTest might be flaky? Tests are passing fine for me locally.