[jeremydmiller]

Closes #5798. Thanks to @gschuager for the report and the design, credited as co-author.

An aggregate projection with a strong-typed identifier auto-registers that type as a DCB tag type. A store that doesn't use DCB still gets a table per identifier, with its foreign key and indexes and a parameter on mt_quick_append_events. The reporter hit ten empty tables moving from 8.38.1 to 9.50.3.

opts.Events.AutoDiscoverTagTypes = false;

• It's on by default, so nothing changes for existing users.
• Explicit RegisterTagType<T>() calls keep working with it off.
• With it off, a tag query fails with the existing "is not registered" message.
• It's a new member on IEventStoreOptions and EventGraph, with no existing signature changed. EventGraph is the only implementation in this repository.

Turning it off on an existing database does not drop tag tables already there. The docs say so.

Verified: with the guard removed, nothing_is_registered_or_built_when_auto_discovery_is_turned_off finds mt_event_tag_ticket_id in information_schema, read from the catalog rather than from configuration. With the guard in place, all 10 tests that ran in the class pass (2 of the 12 were skipped).

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