Global configuration flag for media previews (#29582)

* Modify useMediaVisible to take a room.

* Add initial support for a account data level key.

* Update controls.

* Update settings

* Lint and fixes

* make some tests go happy

* lint

* i18n

* update preferences

* prettier

* Update settings tab.

* update screenshot

* Update docs

* Rewrite controller

* Rewrite tons of tests

* Rewrite RoomAvatar to be a functional component

This is so we can use hooks to determine the setting state.

* lint

* lint

* Tidy up comments

* Apply media visible hook to inline images.

* Move conditionals.

* copyright all the things

* Review changes

* Update html utils to properly discard media.

* Types fix

* Fixing tests that break settings getValue expectations

* Fix logic around media preview calculation

* Fix room header tests

* Fixup tests for timelinePanel

* Clear settings in matrixchat

* Update tests to use SettingsStore where possible.

* fix bug

* revert changes to client.ts

* copyright years

* Add header

* Add a test for MediaPreviewAccountSettingsTab

* Mark initMatrixClient as optional

* Improve on types

* Ensure we do not set the account data twice.

* lint

* Review changes

* Ensure we include the client on rendered messages.

* Fix test

* update labels

* clean designs

* update settings tab

* update snapshot

* copyright

* prevent mutation

src/settings/controllers/MatrixClientBackedController.ts

@@ -26,7 +26,7 @@ export default abstract class MatrixClientBackedController extends SettingContro
         MatrixClientBackedController._matrixClient = client;
 
         for (const instance of MatrixClientBackedController.instances) {
-            instance.initMatrixClient(client, oldClient);
+            instance.initMatrixClient?.(client, oldClient);
         }
     }
 
@@ -40,5 +40,5 @@ export default abstract class MatrixClientBackedController extends SettingContro
         return MatrixClientBackedController._matrixClient;
     }
 
-    protected abstract initMatrixClient(newClient: MatrixClient, oldClient?: MatrixClient): void;
+    protected initMatrixClient?(newClient: MatrixClient, oldClient?: MatrixClient): void;
 }