Add a Mentions room list filter (#5885)

* Add a Mentions room list filter

Adds a new filter chip to the room list that shows only rooms with
unread mentions, using the new mentions room list filter from the
Rust SDK (matrix-org/matrix-rust-sdk branch matthew/mentions-filter).

The SDK version needs bumping to a release that includes the new
filter kind before this can build against the released components.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* Order the room list filters by expected usage

Move Favourites ahead of People and Rooms so the more commonly used
filters (Unreads, Mentions, Favourites) sit first in the chip row —
Rooms and Invites are used rarely enough that it's fine for them to
wrap off the side.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Uk8aPxHn3BHCe52L226jdG

* update the SDK and use the appropriate rust filter types

* preview tests + app settings flag for mentions

---------

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>
Co-authored-by: Mauro Romito <mauro.romito@element.io>

ElementX/Sources/Screens/Settings/DeveloperOptionsScreen/DeveloperOptionsScreenModels.swift

@@ -63,6 +63,7 @@ protocol DeveloperOptionsProtocol: AnyObject {
     
     var fuzzyRoomListSearchEnabled: Bool { get set }
     var lowPriorityFilterEnabled: Bool { get set }
+    var mentionsFilterEnabled: Bool { get set }
     var knockingEnabled: Bool { get set }
     
     var linkPreviewsEnabled: Bool { get set }