Move createAPIFactory to $init() of PluginManager

[tsmaeder]

Signed-off-by: Thomas Mäder tmader@redhat.com

What it does

Fixes Timing issues when starting plugin hosts #8429 by moving the initialization of the ext-side services (for example in createAPIFactory to PluginManagerExtImpl#$init(). In this way, the main-side services (LanguagesMain, etc.) will already be listening when the services try to call them in their constructor (like in TasksExtImpl). Currently, the request to fetch task executions will be silently ignored.

How to test

1. Build Theia
2. Add a front-end and back-end plugin to the installation (for example https://github.com/eclipse/che-theia-samples/tree/master/samples/hello-world-frontend-plugin)
3. Put a breakpoint on line 159 of hosted-plugin-process.ts
4. Start debugging the back-end process (note that front-end plugins are still broken in the electron version, so remove the front end plugin before testing Frontend plugins are broken #6601)
5. Make sure both plugins are activated correctly
6. Make sure the breakpoint is not hit and the error message on that line is not in the log.

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

[tsmaeder]

There are still some complications left here: for example, the WorkspaceMainImpl indirectly calls StorageExt#$updatePluginsWorkspaceData(...). In order to prevent timing issues, there should be a clean three-step initialisation phase:

1. Set up main services, but don't assume ext services are there (except PluginManagerExt)
2. Call PluginManagerExt#$init(). This sets up ext services in the plugin host: they may call main services at this time
3. Start main services: they can assume all ext services are set up.

I probably won't be able to get anywhere before the holidays on this, so making WIP for the time being.