Copies entire project to VSCode workspaceStorage. Doesn't cleanup on Uninstall

[JonathanShor]

Upon opening the single .java file in the repo, this extension (secretly, as far as I'm concerned) copied the entire workspace file tree to VSCode's workspaceStorage. This duplicated 50GB, including (obviously) many files with no relationship to java. Not sure what the rationale for copying every file could be...
but at the very least, clean everything up upon uninstall guys.

Environment

• Operating System: macOS 10.14.5
• JDK version: None!
• Visual Studio Code version: 1.36.1
• Java extension version: latest

[JonathanShor]

Related to #960 and #634 maybe?

[fbricon]

@JonathanShor this kinda relates to those issues but it's a bit different. When you open a single java file, the language server treats its folder as a java source folder, which is then processed in the language server's workspace (in workspaceStorage). the workspace storage is never cleaned because it's faster to reuse it the next time you reopen your folder.

@testforstephen @yaohaizh we should prolly add some filters to the invisible project source folders. Only process java and properties files, with the possibility of configuring additional file types.

[fbricon]

@testforstephen @yaohaizh is there an API to process stuff during extension uninstallation?

[testforstephen]

Looks like there is a thread vscode-45474 to discuss adding an uninstall hook, but it's not supported yet.