Space Tool Improvements 1/2

[philippfromme]

Which issue does this PR address?

• consider moving and non-moving attachers when using space tool
• move external labels with moving shapes/connections
• allow label behavior for laid-out connections (rolls back 393ac63#diff-27fae04affe63769c3cdf53d391a00e3fa209b88c02fa703cf8c6b55155c214dR112 as this isn't the desired behavior)

Breaking Changes

• label behavior for laid-out connection is not disallowed anymore

Related to camunda/camunda-modeler#1750
Child of camunda/camunda-modeler#1753

Space tool improvements 2/2: bpmn-io/bpmn-js#1344

[nikku]

Let us target develop with that change. This is a new feature.

[nikku]

Likely needs another follow up: bpmn-io/bpmn-js#1344 (review)

[philippfromme]

This PR is actually ready to be reviewed.

[nikku]

Then we shall review it. Please move to needs review.

[barmac]

I rebased this on develop.

[barmac]

I run bpmn-js#develop with this PR and 3 test cases fail:

Chrome Headless 106.0.5249.0 (Mac OS 10.15.7) modeling - label layouting integration space tool should NOT adjust / move with a skewed line FAILED
	AssertionError: expected { x: 25, y: 0 } to deeply equal { x: 0, y: 0 }
	    at expectLabelMoved (webpack-internal:///./test/spec/features/modeling/LabelLayoutingSpec.js:584:20)
	    at eval (webpack-internal:///./test/spec/features/modeling/LabelLayoutingSpec.js:551:9)
	    at Modeler.invoke (webpack-internal:///../diagram-js/node_modules/didi/dist/index.esm.js:232:15)
	    at Context.eval (webpack-internal:///./test/helper/index.js:246:20)
.........................................................................
Chrome Headless 106.0.5249.0 (Mac OS 10.15.7) features/modeling - create/remove space create space should create space to the left FAILED
	AssertionError: expected <SequenceFlow_3_label> position to equal
	  { x: 147, y: 204 }
	but got
	  { x: 168, y: 204 }
Chrome Headless 106.0.5249.0 (Mac OS 10.15.7) features/modeling - create/remove space case 1 should create space to the left FAILED
	AssertionError: expected <SequenceFlow_C_label> position to equal
	  { x: 477, y: 233 }
	but got
	  { x: 437, y: 412 }

Let's investigate whether we are introducing breaking changes in the PR or the tests are too rigid and assure a buggy behaviour.

[philippfromme]

3 test cases fail:

These 3 tests are failing because 4851c17 is a breaking change. They all expect connection labels not to be moved when the connection is laid out. That is not the expected behavior:

The expected behavior is this:

If only the source or target of a connection is moved the connection is laid out. If both source and target move, the connection is moved.

I marked the commit introducing the breaking change: 4851c17