Add a banner to encrypted rooms with visible history. (#4738)

* feat: Add history visible alert.

- Adds a dismissable alert that is displayed whenever the user
  opens a room with `history_visibility` != `joined`. When cleared,
  this is recorded in the app's data store.
- When opening a room with `history_visibility` = `joined`, this
  flag is cleared.

Issue: element-hq/element-meta#2875

* tests: Add unit tests for history sharing in `RoomScreenFooterView`.

* feat: Rename flag to `hasSeenHistoryVisibleBannerRooms`, document.

* refactor: Merge enum variants, use function for banner description.

* feat: Use `AppSettings.historyVisibleDetailsURL` over hard-coded value.

* tests: Correct potential race condition with deferred assertion.

* chore: Use Localazy translation string over project-defined.

* fix: Final tweaks and review comments.

* chore: Checkout `Enterprise` submodule.

* tests: Final fixes.

UnitTests/Sources/AuthenticationStartScreenViewModelTests.swift

@@ -172,6 +172,7 @@ class AuthenticationStartScreenViewModelTests: XCTestCase {
                              deviceVerificationURL: appSettings.deviceVerificationURL,
                              chatBackupDetailsURL: appSettings.chatBackupDetailsURL,
                              identityPinningViolationDetailsURL: appSettings.identityPinningViolationDetailsURL,
+                             historyVisibleDetailsURL: appSettings.historyVisibleDetailsURL,
                              elementWebHosts: appSettings.elementWebHosts,
                              accountProvisioningHost: appSettings.accountProvisioningHost,
                              bugReportApplicationID: appSettings.bugReportApplicationID,