Mdns has no shutdown flow

[kpschoedel]

Problem

#9108 recently added ChipMdnsShutdown() to fix crashing unit tests (#8001), but this is currently only used by unit tests and not normal flow, because the normal caller itself has no shutdown path.

Proposed Solution

Plumb shutdown through mdns.

[bzbarsky-apple]

Per #8001, this means that shutting down the CHIP stack after using mdns bits can crash. This is not really OK.

@andy31415 @cecille

[woody-apple]

SDK Review: This sounds like a required 1.0 fix, but does not affect SVE, removing the request SVE label.

[woody-apple]

Issue Scrub: Moving this to maintainability.

[stale[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs.