[Gradle 9] Fixed Gradle 9 Deprecations in Packages

[jesswrd]

Fixed all Gradle 9 deprecations in packages repo.

Fixes flutter/flutter#173320
Partially Adresses flutter/flutter#173318

Pre-Review Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
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• The title of the PR starts with the name of the package surrounded by square brackets, e.g. [shared_preferences]
• I linked to at least one issue that this PR fixes in the description above.
• I updated pubspec.yaml with an appropriate new version according to the pub versioning philosophy, or I have commented below to indicate which version change exemption this PR falls under¹.
• I updated CHANGELOG.md to add a description of the change, following repository CHANGELOG style, or I have commented below to indicate which CHANGELOG exemption this PR falls under¹.
• I updated/added any relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or I have commented below to indicate which test exemption this PR falls under¹.
• All existing and new tests are passing.

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[flutter-dashboard]

It looks like this pull request may not have tests. Please make sure to add tests or get an explicit test exemption before merging.

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[gemini-code-assist]

Code Review

This pull request updates various Gradle build files to fix deprecations for Gradle 9. The changes primarily involve updating the Groovy DSL syntax to use property assignment, replacing the deprecated jcenter() repository with mavenCentral(), and updating the Kotlin Gradle plugin version. The changes are mostly correct and address the goal of the PR. I've found one area for improvement regarding a redundant buildscript block in one of the settings files.

[reidbaker]

These changes look good but we dont have anything in this pr preventing regressions back to using the space assignment syntax. It doesnt need to be in this pr but consider modifying gradle check to enforce some of these changes.

[domesticmouse]

LGTM once @reidbaker's concerns are dealt with