Detect updated JAVA_HOME and modify bloop configuration accordingly

[here-abarany]

Is your feature request related to a problem? Please describe.

When updating the Java installation location, the bloop configuration retains the original installation path, causing the build to fail the next time the project is opened.

Describe the solution you'd like

Detect when the Java installation path changes, either with an explicit user/workspace config or implicitly through JAVA_HOME, and update the bloop configurations accordingly.

Describe alternatives you've considered

Deleting the .bloop, .metals, and target folders throughout the source tree to fully reset the Metals project. This may require going through multiple sub-directories (e.g. the project folder for an SBT project) to get all of them.

Additional context

This is very common to occur on Windows, since the JDK installation location typically includes the full semantic version. In other words, even a small update that simply increments the patch version will cause the installation location to change, and break any projects using Metals.

Search terms

JAVA_HOME update

[tgodzik]

If you modify the metals.javaHome it should pick it up and suggest to restart. Otherwise, you should be able to see in the metals vscode logs how it's picking the java version

[here-abarany]

If you modify the metals.javaHome it should pick it up and suggest to restart.

I can verify that providing metals.javaHome does update the bloop config. However, since it is able to detect Java from the environment variables automatically on initial setup, it would be much more convenient to be able to update that automatically when it changes rather than having to manually update the path every time there's an update. None of the actions I tried, including "Clean and restart build server", was able to get it to update the config without deleting the generated files entirely in that case.