Add a Push rules entry to the developer options

Add a "Push rules" item in the Notifications section of the developer options,
above "Push history". It displays the raw push rules of the account, which were
only available as a rageshake attachment so far.

The content is read using NotificationSettingsService.getRawPushRules(), then
rendered by the new FileViewerEntryPoint, so that the screen looks like the media
viewer rendering a file, with Share and Download actions on a
push_rules<userId>.json file. The user id contains a colon, which is not a valid
file name character on all the file systems, so it is replaced by an underscore.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

features/preferences/impl/build.gradle.kts

@@ -64,6 +64,7 @@ dependencies {
     implementation(projects.libraries.testtags)
     implementation(projects.libraries.uiStrings)
     implementation(projects.libraries.matrixui)
+    implementation(projects.libraries.mediaviewer.api)
     implementation(projects.libraries.mediapickers.api)
     implementation(projects.libraries.mediaupload.api)
     implementation(projects.libraries.permissions.api)
@@ -108,6 +109,7 @@ dependencies {
     testImplementation(projects.libraries.push.test)
     testImplementation(projects.libraries.pushstore.test)
     testImplementation(projects.libraries.roomselect.test)
+    testImplementation(projects.libraries.mediaviewer.test)
     testImplementation(projects.libraries.troubleshoot.test)
     testImplementation(projects.features.deactivation.test)
     testImplementation(projects.features.enterprise.test)