replace java and debug native with vscode extensions

[akosyakov]

Motivated by #6113 (comment)

• theia-apps should be updated: use vscode extensions instead of native theia-ide/theia-apps#239
• java, java-debug, nodes-debug extensions should be removed and replaced by auto-downloading corresponding vscode extensions into plugins folder for testing purporses with example apps
• a record in CHANGELOG should be added to explain for end products:
  • how to switch to use vscode extensions
  • how to use yarn resolutions to keep using old native extensions

cc @marcdumais-work

[vince-fugnitto]

Do we want to clean up before this week's release?

[akosyakov]

@vince-fugnitto i don't think anyone on our side has time for, if you can go ahead, if not we can do it later

[tsmaeder]

Make sure to not download from the vscode marketplace. It's a no-no.

[marcdumais-work]

@tsmaeder small typo I think: "now" -> "not", but the idea is correct. We can use the links currently in place in the theia extensions, that pull from GitHub releases:

https://github.com/eclipse-theia/theia/blob/master/packages/debug-nodejs/package.json#L52-L53
https://github.com/eclipse-theia/theia/blob/master/packages/java-debug/package.json#L53

edit: Or vscode built-in extension(s) if appropriate, which may be the case for node-debug IIUC.

[vince-fugnitto]

Closed by #6933