Feature: Block Grid inline editing + Extension Initializers change

[nielslyngsoe]

This PR finalises the feature of Block Grid Inline Editing, which has never reached this point before, though there have been Prove of concept available.

Also notice this contains updates to Core functionality.
This PR changes Extension Initializers so they do no longer clean up extension on host disconnected. — Instead extensions gets updated in the aftermath of begin re-connected to a host. This enables things that are begin dragged around to not be disassembled and reassembled when moved around.

The reason for the change and the actual change of this PR:
The Extension Initializer did reset when manifest changed, or when hostDisconnected. This turned out not to be so great when dragging Blocks around in Block Grid Editor. Cause then a Block gets disconnected.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Chore (minor updates related to the tooling or maintenance of the repository, does not impact compiled assets)

Motivation and context

How to test?

Screenshots (if appropriate)

Checklist

• If my change requires a change to the documentation, I have updated the documentation in this pull request.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.