Support 2024.2 eap

[jansorg]

Closes https://github.com/getappmap/appmap-intellij-plugin/issues/717

Adds compatibility with 2024.2 eap. This time, supporting the new EAP is a bit painful. It requires a new Gradle build setup (using a beta version of a new Gradle plugin) and JetBrains clarified the internal API in the new major version.

• Because 2024.2 requires a new build setup, this PR is migrating to the new Gradle build setup.
• CI is now using Java 21, because 2024.2 migrated from Java 17 to 21
• Indexing is now async in tests with 2024.2. We're changing our tests to wait until indexing finished because we rely on indexes.
• In the build setup, we're working around a few problems of the new intellij-platform-gradle plugin, we'll remove them as soon as the plugin is fixed

[github-actions[bot]]

AppMap runtime code review

Summary	Status
Failed tests	:white_check_mark: All tests passed
API changes	:zero: No API changes
Security flaws	:white_check_mark: None detected
Performance problems	:white_check_mark: None detected
Code anti-patterns	:white_check_mark: None detected
New AppMaps	:zero: No new AppMaps

[appland-release]

:tada: This issue has been resolved in version 0.70.0 :tada:

The release is available on:

• v0.70.0
• GitHub release

Your semantic-release bot :package::rocket: