fix(schema): improve default title resolution for references

[bjoerge]

Description

When no title is given for a referenced document type, we currently default to the type name as-is, which makes the UI less user friendly (as pointed out in #3046).

This PR fixes it so that we display the referenced type in this order:

• The title defined for the referenced type at the reference field/array item, if any
• The title specified for the referenced document type, if any
• A startCase'd version of the referenced document's type name (note: this follows from how we already resolve the default title for object types)

What to review

Verify that the UI displays titles of reference fields and array items in a user friendly way

Notes for release

• Made the default title of referenced document types more user friendly

Fixes #3046

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perf-studio – ./

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test-studio – ./

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studio-workshop – ./dev/workshop

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[rexxars]

Needs a rebase, but looks good from what I can tell!