Create MWLiveExtensionInspector base class

Most of the code stolen from MWMathInspector and genericised.

Also fix issues with fragment not wrapping the new node correctly.

Bug: 58286
Bug: 58045
Change-Id: I708c4cb012becf8c493d5b65a051c0b13f7a11ac
Make Hiero node live update

Just change inheritence.

Change-Id: Id63f545d16a478e336ddeb6cc8f1a31c88ee1aaa
Merge "Create MWLiveExtensionInspector base class"
Merge "Make Hiero node live update"