fix: (device_info_plus): Migrate Plugin to Built-in Kotlin

[ravi84184]

Description

Related Issues

Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I titled the PR using Conventional Commits.
• I did not modify the CHANGELOG.md nor the plugin version in pubspec.yaml files.
• All existing and new tests are passing.
• The analyzer (flutter analyze) does not report any problems on my PR.

Breaking Change

Does your PR require plugin users to manually update their apps to accommodate your change?

• Yes, this is a breaking change (please indicate that with a ! in the title as explained in Conventional Commits).
• No, this is not a breaking change.

[mdmahendri]

I initially considered combining these steps in #3858, but I realized that keeping the addition of new features/configurations in a separate PR makes it much cleaner for maintainers to review.
Regarding the build files: while we can technically migrate to built-in Kotlin while keeping the Groovy DSL layout, we should heavily prioritize migrating fully to Kotlin DSL build.gradle.kts as a first step. Moving away from Groovy eliminates legacy deprecation risks and establishes proper type-safety as we upgrade AGP versions.
As noted in the Android Developer documentation:

Starting with Android Studio Giraffe, new projects use the Kotlin DSL (build.gradle.kts) by default for build configuration. This offers a better editing experience than the Groovy DSL (build.gradle) with syntax highlighting, code completion, and navigation to declarations.