Replace RxJava in extension installer (#9556)

* Replace RxJava in extension installer

Replace common downloadsRelay with Map of individual StateFlows

* Drop RxRelay dependency

* Simplify updateAllExtensions

* Simplify addDownloadState/removeDownloadState

Use immutable Map functions instead of converting to MutableMap

app/src/main/java/eu/kanade/tachiyomi/extension/ExtensionManager.kt

@@ -14,10 +14,11 @@ import eu.kanade.tachiyomi.extension.util.ExtensionLoader
 import eu.kanade.tachiyomi.util.preference.plusAssign
 import eu.kanade.tachiyomi.util.system.toast
 import kotlinx.coroutines.async
+import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.asStateFlow
+import kotlinx.coroutines.flow.emptyFlow
 import logcat.LogPriority
-import rx.Observable
 import tachiyomi.core.util.lang.launchNow
 import tachiyomi.core.util.lang.withUIContext
 import tachiyomi.core.util.system.logcat
@@ -200,7 +201,7 @@ class ExtensionManager(
      *
      * @param extension The extension to be installed.
      */
-    fun installExtension(extension: Extension.Available): Observable<InstallStep> {
+    fun installExtension(extension: Extension.Available): Flow<InstallStep> {
         return installer.downloadAndInstall(api.getApkUrl(extension), extension)
     }
 
@@ -211,9 +212,9 @@ class ExtensionManager(
      *
      * @param extension The extension to be updated.
      */
-    fun updateExtension(extension: Extension.Installed): Observable<InstallStep> {
+    fun updateExtension(extension: Extension.Installed): Flow<InstallStep> {
         val availableExt = _availableExtensionsFlow.value.find { it.pkgName == extension.pkgName }
-            ?: return Observable.empty()
+            ?: return emptyFlow()
         return installExtension(availableExt)
     }