[plugin] Added extensionDependency automatically downloading. Fixes: #4504

[JPinkney]

This PR enables VSCode extension dependencies that comes from package.json.

You can test by using deploy by plugin id command with vscode:extension/vscjava.vscode-java-debug and vscode-java will automatically be installed before vscjava.vscode-java-debug is.

Fixes: #4504

Signed-off-by: Josh Pinkney joshpinkney@gmail.com

[akosyakov]

Should not it be a part of the vscode plugin resolver without any other changes? It could add a current extension, then look at it package.json, find dependencies, download them, unarchive them and then apply itself recursively till all dependencies are collected.

Otherwise it looks like a broken abstraction, since plugin system assumes that any dependency should be resolved as a vscode extension.

cc @evidolob @benoitf

[JPinkney]

@akosyakov I've just fixed it up so that it almost entirely lives in the VSCode plugin resolver, if you don't mind reviewing again!

[tsmaeder]

@benoitf @akosyakov what do we need to do to move this PR forward?

[akosyakov]

Code looks good, i had some remarks please have a look.

@tsmaeder it should be rebased and add a notice which extension to use to test it. Someone can test after fixing remarks and rebasing.

[akosyakov]

Code wise it looks good to me and worked very well as well 👍

@JPinkney i will let it sit for today and merge tomorrow morning, just in case if @theia-ide/plugin-system want to check changes to the deployment logic

It would be good to nominate your as a committer as well! I hope @tsmaeder can do it, if not let me know i will do.