Remove dependency injection from core module and data module from presentation-widget module

Includes side effects:
- No longer need to restart app for user agent string change to take effect
- parseAs extension function requires a Json instance in the calling context, which doesn't necessarily need to be the default one provided by Injekt

app/src/main/java/eu/kanade/tachiyomi/extension/api/ExtensionGithubApi.kt

@@ -11,6 +11,7 @@ import eu.kanade.tachiyomi.network.NetworkHelper
 import eu.kanade.tachiyomi.network.awaitSuccess
 import eu.kanade.tachiyomi.network.parseAs
 import kotlinx.serialization.Serializable
+import kotlinx.serialization.json.Json
 import logcat.LogPriority
 import tachiyomi.core.preference.Preference
 import tachiyomi.core.preference.PreferenceStore
@@ -24,10 +25,12 @@ internal class ExtensionGithubApi {
 
     private val networkService: NetworkHelper by injectLazy()
     private val preferenceStore: PreferenceStore by injectLazy()
+    private val extensionManager: ExtensionManager by injectLazy()
+    private val json: Json by injectLazy()
+
     private val lastExtCheck: Preference<Long> by lazy {
         preferenceStore.getLong("last_ext_check", 0)
     }
-    private val extensionManager: ExtensionManager by injectLazy()
 
     private var requiresFallbackSource = false
 
@@ -53,9 +56,11 @@ internal class ExtensionGithubApi {
                     .awaitSuccess()
             }
 
-            val extensions = response
-                .parseAs<List<ExtensionJsonObject>>()
-                .toExtensions()
+            val extensions = with(json) {
+                response
+                    .parseAs<List<ExtensionJsonObject>>()
+                    .toExtensions()
+            }
 
             // Sanity check - a small number of extensions probably means something broke
             // with the repo generator