[4.0] Break up tags code from category interface

[wilsonge]

Pull Request for Issue #24587 .

Summary of Changes

Breaks up tags code from the interface and adds a corresponding trait.

Note as it shares methods with the CategoryServiceTrait we have to choose to prioritize one of the methods (as they are identical I've arbitrarily chosen CategoryServiceTrait but there's no deeper reasoning for that decison)

Testing Instructions

Check the count of items associated with a tag continues to work in the tags component when you filter by a tag type (e.g. article)

Documentation Changes Required

Yup. New tag interface needs to be documented

[alikon]

played with tags and article and article category...... lgtm

[alikon]

I have tested this item ✅ successfully on af0ec82

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[jwaisner]

I have tested this item ✅ successfully on af0ec82

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[jwaisner]

RTC

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[wilsonge]

Thanks!