Backport #21910 to V13

[kjac]

Prerequisites

• I have added steps to test this contribution in the description below

Description

This is a partial backport of #21910 to V13. Partial because the cache redo for V15 is logically not applicable here 😄

The PR still classifies changes as "structural" or "non-structural". See #21910 for details.

Test results

I've been testing this on a local database with ~10000 pages of the same content type.

• Without this PR, any content type change takes ~13 seconds to complete.
• With this PR, a structural change still takes ~13 seconds to complete (no changes), but a non-structural change only takes ~0.04 seconds to complete (it is now reduced to a simple save operation).

[AndyButland]

Code looks good and aligned with what you did on 17 in the linked PR @kjac, but I've found an issue I believe with removing property types. These are coming out as RefreshOther, which isn't correct.

If I debug line 229 in ContentTypeServiceBase:

var hasAnyPropertyBeenRemoved = dirty.WasPropertyDirty("HasPropertyTypeBeenRemoved");

hasAnyPropertyBeenRemoved is false if I remove a property from the document type.

[kjac]

My bad, @AndyButland 🙈 I forgot to push the backport of #21856, which was a prerequisite for #21910 in V17. It's pushed now.

[AndyButland]

All looks good now, though I was still finding the the removal of a property wasn't leading to the expected RefreshMain change type. I think I found the fix though, and demonstrated it with a failing and now passing integration test - so have pushed that up. Please take a look to make sure it makes sense to you before merging.

Otherwise I've tested the various scenarios of property add/removal, document type name, alias changes, composition and variance changes - and all yield the expected.