Simplify push notification flow by using locally stored values for pending pushes (#6258)

* Create `PushRequest` in push history DB: this will be used to store requests for push notifications, either pending or completed ones.

* Rename `WorkManagerRequest` to `WorkManagerRequestBuilder`: make its `build` method return a list of `WorkManagerRequestWrapper`, which can be used to enqueue normal or unique workers.

* Rename `PerformDatabaseVacuumRequestBuilder` and adapt it to the new API.

* Adjust other components using `WorkManagerRequest`.

* Replace `SyncNotificationWorkManagerRequestBuilder` with `SyncPendingNotificationsRequestBuilder` and `FetchNotificationsWorker` with `FetchPendingNotificationsWorker`: this new pair of request builder and worker allow enqueuing requests for a session id and, once the worker runs, retrieve all the pending request data and use it to fetch the associated events. This simplifies quite a bit how this data had to be passed or grouped, since it's no longer necessary to do so

* Add new methods to `PushHistoryService` to modify the `PushDatabase`:

- insertOrUpdatePushRequest
- insertOrUpdatePushRequests
- getPendingPushRequests
- removeOldPushRequests

* Make `PushHandler` just handle incoming pushes: those will be inserted into the pending push request table in DB, then handled by the new worker. Once the process finished, a new `NotificationResultProcessor` will handle the results and what needs to be done with them (call ringing, displaying notifications, etc.)

* Add `requestType` optional parameter to `WorkManagerScheduler.cancel` so we can decide to only cancel some kinds of requests.

* Add migration to remove existing work manager requests for fetching notifications, since the previous worker class no longer exists.

features/migration/impl/build.gradle.kts

@@ -31,6 +31,7 @@ dependencies {
     implementation(projects.libraries.matrix.api)
     implementation(projects.libraries.sessionStorage.api)
     implementation(projects.libraries.uiStrings)
+    implementation(projects.libraries.workmanager.api)
 
     testCommonDependencies(libs)
     testImplementation(projects.libraries.matrix.test)

features/migration/impl/src/main/kotlin/io/element/android/features/migration/impl/migrations/AppMigration10.kt

@@ -0,0 +1,39 @@
+/*
+ * Copyright (c) 2026 Element Creations Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.features.migration.impl.migrations
+
+import dev.zacsweers.metro.AppScope
+import dev.zacsweers.metro.ContributesIntoSet
+import io.element.android.libraries.matrix.api.core.SessionId
+import io.element.android.libraries.sessionstorage.api.SessionStore
+import io.element.android.libraries.workmanager.api.WorkManagerRequestType
+import io.element.android.libraries.workmanager.api.WorkManagerScheduler
+
+/**
+ * Remove existing fetch notifications work manager requests since their format has changed.
+ */
+@ContributesIntoSet(AppScope::class)
+class AppMigration10(
+    private val sessionStore: SessionStore,
+    private val workManagerScheduler: WorkManagerScheduler,
+) : AppMigration {
+    override val order: Int = 10
+
+    override suspend fun migrate(isFreshInstall: Boolean) {
+        if (isFreshInstall) return
+
+        val sessions = sessionStore.getAllSessions()
+
+        for (session in sessions) {
+            workManagerScheduler.cancel(
+                sessionId = SessionId(session.userId),
+                requestType = WorkManagerRequestType.NOTIFICATION_SYNC
+            )
+        }
+    }
+}