Selection position is lost when unwrapping range

[Reinmar]

setModelData(
	doc,
	'<heading>a[bc</heading>' +
	'<messageQuote><paragraph>x]x</paragraph></messageQuote>' +
	'<paragraph>def</paragraph>'
);

batch.unwrap( quote );

console.log( getModelData( doc ) ); // <heading>a[bc</heading><paragraph>xx</paragraph>]<paragraph>def</paragraph>

[Reinmar]

I also get:

<messageQuote><heading>a[bc</heading><paragraph>def</paragraph><paragraph>xx</paragraph>]</messageQuote><paragraph>ghi</paragraph>

For this content:

setModelData(
	doc,
	'<heading>a[bc</heading>' +
	'<paragraph>def</paragraph>' +
	'<messageQuote><paragraph>x]x</paragraph></messageQuote>' +
	'<paragraph>ghi</paragraph>'
);

And this:

[<messageQuote><paragraph>abc</paragraph></messageQuote><widget>xx</widget>]<messageQuote><paragraph>def</paragraph></messageQuote>

When wrapping both paragraphs separately:

<paragraph>a[bc</paragraph><widget>xx</widget><paragraph>de]f</paragraph>

[Reinmar]

I pushed t/841 with tests. All red :D

[Reinmar]

I feel I'll need this many times, so a snippet for debugging this:

import { stringify } from '../dev-utils/model';

result[ 0 ] && console.log( 0, changeType, deltaType, stringify( result[ 0 ].root, result[ 0 ] ) );
result[ 1 ] && console.log( 1, changeType, deltaType, stringify( result[ 1 ].root, result[ 1 ] ) );
result[ 2 ] && console.log( 2, changeType, deltaType, stringify( result[ 2 ].root, result[ 2 ] ) );

[Reinmar]

t/841 contains a potential fix for this issue now, but I'd need to add a few tests in the range itself (e.g. for getTransformedByDelta()) or move the current ones there before it could be merged, so I'll first work on the message quote feature to validate these changes.