Reapply "Fix thread starvation caused by not yielding or using an inappropriate thread pool (#2955)"

This reverts commit 1d7c838ae6.

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

@@ -23,6 +23,7 @@ import kotlinx.coroutines.flow.asStateFlow
 import kotlinx.coroutines.flow.emptyFlow
 import kotlinx.coroutines.flow.map
 import kotlinx.coroutines.flow.stateIn
+import kotlinx.coroutines.launch
 import logcat.LogPriority
 import tachiyomi.core.common.util.lang.withUIContext
 import tachiyomi.core.common.util.system.logcat
@@ -118,17 +119,19 @@ class ExtensionManager(
      * Loads and registers the installed extensions.
      */
     private fun initExtensions() {
-        val extensions = ExtensionLoader.loadExtensions(context)
+        scope.launch {
+            val extensions = ExtensionLoader.loadExtensions(context)
 
-        installedExtensionMapFlow.value = extensions
-            .filterIsInstance<LoadResult.Success>()
-            .associate { it.extension.pkgName to it.extension }
+            installedExtensionMapFlow.value = extensions
+                .filterIsInstance<LoadResult.Success>()
+                .associate { it.extension.pkgName to it.extension }
 
-        untrustedExtensionMapFlow.value = extensions
-            .filterIsInstance<LoadResult.Untrusted>()
-            .associate { it.extension.pkgName to it.extension }
+            untrustedExtensionMapFlow.value = extensions
+                .filterIsInstance<LoadResult.Untrusted>()
+                .associate { it.extension.pkgName to it.extension }
 
-        _isInitialized.value = true
+            _isInitialized.value = true
+        }
     }
 
     /**