Send correct receipts when viewing a room (#10864)

* Send correct receipts when viewing a room

* Fix strict type issues

* Handle promises

* Handle more primises

* Add generic array type

* Replace existende check with type predicate

* Fix wrong variable check

* Improve comment about initial read marker

* Use read_markers API for fully read receipts

* Log public receipt fallback

* Rename variables in new code to be aligned to the spec

* Add end-2-end test for read markers and receipts

test/test-utils/test-utils.ts

@@ -175,7 +175,7 @@ export function createTestClient(): MatrixClient {
         decryptEventIfNeeded: () => Promise.resolve(),
         isUserIgnored: jest.fn().mockReturnValue(false),
         getCapabilities: jest.fn().mockResolvedValue({}),
-        supportsThreads: () => false,
+        supportsThreads: jest.fn().mockReturnValue(false),
         supportsIntentionalMentions: () => false,
         getRoomUpgradeHistory: jest.fn().mockReturnValue([]),
         getOpenIdToken: jest.fn().mockResolvedValue(undefined),