Introduced config dir on the env variable server

[kittaakos]

Follow-up of #6650.

What it does

From now on, all configuration (settings.json, keymaps.json, etc) and VS Code extension things (such as globalStorage, logs, and plugin-storage) goes directly under the configuration folder.
Downstream projects can override the default, .theia folder name for the configurations. See the example here.

What it does not do:

• we do not distinguish between cachable (XDG_CACHE_HOME on Linux and AppData/Local on Windows, such as workspace storage, extensions and their logs for example) and shareable things (XDG_CONFIG_HOME on Linux and AppData/Roaming on WIndows, such as settings.json, keymaps.json)

How to test

Try the example customization:

• try to run a task from a workspace location (note, tasks.json should go under .theia-example),
• see you have the .theia-example folder under ~/,
• POSIX: you can open recent workspaces and see if the paths are still correctly tildyfied.

Review checklist

• as an author, I have thoroughly tested my changes and carefully followed the review guidelines

Reminder for reviewers

• as a reviewer, I agree to behave in accordance with the review guidelines

[kittaakos]

Note, once the review is over, I am going to drop 8ab1980 from this PR.

[akosyakov]

It looks weird, fsPath should not have scheme already. How can I get URI leading to such case. I think some clients are likely to be bogus.

[kittaakos]

No idea, I reused the previous changes.

[akosyakov]

@mmorhun Could you give a hint? It looks like there is a bug in how some client constructs URI. We should not expect such fs paths.

[akosyakov]

let's remove it, if there will be a regression, we will fix it properly.

[mmorhun]

@akosyakov I added that code as a quick fix. I agree that this is a kludge and we have to find proper solution. The reason I added it was that FileUri.fsPath, was returning wrong path: /file:/right/path.

[akosyakov]

@mmorhun it can happen only if a uri passed to FileUri.fsPath is bogus, the real issue is to figure how one get such bogus URI and fix the producer

[akosyakov]

@kittaakos please squash not your commits in one commit, all of them are fixing issues in the original commit. It is alright since the authorship will be preserved.

[kittaakos]

@akosyakov, I have fixed the build, the tests, and updated the changelog. This PR is ready for review.

CC: @benoitf

[akosyakov]

It works well and thank you for cleaning up everything!

I've tried to change between .my-theia and .theia several times with different set of core and plugin configurations and it worked nicely.