Bug: Incorrect plugin insertion order in settings.gradle with pluginManagement and buildscript

[div-bargali]

What's changed?

Added failing unit tests to demonstrate incorrect plugin ordering in settings.gradle[.kts] files when both pluginManagement and buildscript blocks are present.

New tests added:

• addPluginWithPluginManagementAndBuildscriptBlocks() - Groovy DSL test
• addPluginWithPluginManagementAndBuildscriptBlocksKotlin() - Kotlin DSL test

These tests currently fail because AddPluginVisitor incorrectly inserts the plugins block between pluginManagement and buildscript, violating Gradle's required ordering.

What's your motivation?

• Closes Bug: Incorrect plugin insertion order in settings.gradle with pluginManagement and buildscript #6479

When AddSettingsPlugin is applied to a settings.gradle file containing both pluginManagement and buildscript blocks, it produces invalid Gradle syntax that causes build failures with the error:
only buildscript {} and other plugins {} script blocks are allowed before plugins {} block

Anything in particular you'd like reviewers to focus on?

• Verify that the test cases accurately represent the expected Gradle ordering requirements
• Confirm that both Groovy and Kotlin DSL tests properly cover the edge case
• Review the interpolateResolvedVersionKotlin() helper method for Kotlin tests

Any additional context

This PR includes the failing tests to document the bug before implementing the fix. The fix will be submitted in a follow-up commit.

Impact: This issue affects any project using AddSettingsPlugin on settings files that contain both pluginManagement and buildscript blocks.

Checklist

• I've added unit tests to cover both positive and negative cases
• I've read and applied the recipe conventions and best practices
• I've used the IntelliJ IDEA auto-formatter on affected files

[timtebeek]

Thanks for getting this started @div-bargali ; At first glance these tests look good to me!

[shanman190]

Both tests also look good to me too!

[div-bargali]

Added the fix for the bug @timtebeek.

I also noticed that in the Kotlin script handling section, the AST was parsed incorrectly for the (.kts) files. Due to this, the kotlin login in AddPluginVistor was not working correctly for build.gradle.kts file. I was able to assert that by adding a simple-but-missing test in AddBuildPluginTest class.

I have included the fix for that too in this PR.

[timtebeek]

Thanks a lot for the help here @div-bargali ; that a parallel effort was started accidentally only speaks to that you've picked a worthwhile issue to fix, and I like the approach you took here.