Fix process watcher path detection

[nickbeattie]

This pull request enhances the logic for determining the Java Runtime Environment (JRE) home in the ProcessWatcher class, prioritizing user-configured settings and improving fallback mechanisms. It also introduces a utility method to validate JDK paths. Below are the key changes:

Improvements to JRE home detection:

• Added logic to prioritize the java.jdt.ls.java.home setting if explicitly configured by the user. If the configured path is invalid, a warning is logged, and fallback options are considered. (src/daemon/processWatcher.ts, src/daemon/processWatcher.tsL37-R74)
• Extended fallback mechanisms to check the java.configuration.runtimes setting for a default runtime or the first available runtime if no default is set. (src/daemon/processWatcher.ts, src/daemon/processWatcher.tsL37-R74)
• Retained the embedded JRE as the final fallback option if no valid JRE is found in user settings. (src/daemon/processWatcher.ts, [1] [2]

Utility method for JDK path validation:

• Introduced a new private method isValidJpsPath to check if a given JDK path is valid by verifying its existence and the presence of the jps tool in the bin directory. (src/daemon/processWatcher.ts, src/daemon/processWatcher.tsR137-R151)

[nickbeattie]

@microsoft-github-policy-service agree

[testforstephen]

@nickbeattie thanks for your contribution. Could you help explain what issue you want to address with this PR?

[nickbeattie]

The company I work for uses Santa for binary authentication. We need to provide a custom Java runtime so that we don't continuously get popups. This PR addresses that by using the alternative JDK/JREs provided by the Java plugin settings.

[testforstephen]

What pop-ups are you seeing? The JRE lookup in src/daemon/processWatcher.ts is only used for a heartbeat check and shouldn’t affect any functionality.

[nickbeattie]

The popup doesn't come from the plugin; it comes from Santa (link above in my previous comment). This causes an obstructive popup for our engineers.

[testforstephen]

@nickbeattie LGTM. thank you for contribution.