Use Flow in ExtensionManager and SourceManager (#7547)

- Replace ExtensionManager relay and observable with Flow
- Inverse SourceManager dependency
    - SourceManager observers ExtensionManager flow
- Separate SourceData from SourceRepository as it created a circular dependency

app/src/main/java/eu/kanade/domain/extension/interactor/GetExtensionLanguages.kt

@@ -14,7 +14,7 @@ class GetExtensionLanguages(
     fun subscribe(): Flow<List<String>> {
         return combine(
             preferences.enabledLanguages().asFlow(),
-            extensionManager.getAvailableExtensionsObservable().asFlow(),
+            extensionManager.getAvailableExtensionsFlow(),
         ) { enabledLanguage, availableExtensions ->
             availableExtensions
                 .map { it.lang }

app/src/main/java/eu/kanade/domain/extension/interactor/GetExtensionUpdates.kt

@@ -1,6 +1,5 @@
 package eu.kanade.domain.extension.interactor
 
-import eu.kanade.core.util.asFlow
 import eu.kanade.tachiyomi.data.preference.PreferencesHelper
 import eu.kanade.tachiyomi.extension.ExtensionManager
 import eu.kanade.tachiyomi.extension.model.Extension
@@ -15,7 +14,7 @@ class GetExtensionUpdates(
     fun subscribe(): Flow<List<Extension.Installed>> {
         val showNsfwSources = preferences.showNsfwSource().get()
 
-        return extensionManager.getInstalledExtensionsObservable().asFlow()
+        return extensionManager.getInstalledExtensionsFlow()
             .map { installed ->
                 installed
                     .filter { it.hasUpdate && (showNsfwSources || it.isNsfw.not()) }

app/src/main/java/eu/kanade/domain/extension/interactor/GetExtensions.kt

@@ -19,9 +19,9 @@ class GetExtensions(
 
         return combine(
             preferences.enabledLanguages().asFlow(),
-            extensionManager.getInstalledExtensionsObservable().asFlow(),
-            extensionManager.getUntrustedExtensionsObservable().asFlow(),
-            extensionManager.getAvailableExtensionsObservable().asFlow(),
+            extensionManager.getInstalledExtensionsFlow(),
+            extensionManager.getUntrustedExtensionsFlow(),
+            extensionManager.getAvailableExtensionsFlow(),
         ) { _activeLanguages, _installed, _untrusted, _available ->
 
             val installed = _installed