Android: Get rid of the per-platform styles, as we only using the GC one.

I think the intention might have been to switch styles based on what
platform was selected, but that never happened. Instead, everything just
used the GC styles.

All the platform-specific styles did was add an accent color (which
tints the checkbox and text area elements). This adds a specific color for
that instead of abusing a platform color.

There should be no visual changes for this commit.

Source/Android/app/src/main/AndroidManifest.xml

@@ -31,7 +31,7 @@
 
         <activity
             android:name=".ui.main.MainActivity"
-            android:theme="@style/DolphinGamecube">
+            android:theme="@style/DolphinBase">
 
             <!-- This intentfilter marks this Activity as the one that gets launched from Home screen. -->
             <intent-filter>
@@ -43,7 +43,7 @@
 
         <activity
             android:name=".ui.main.TvMainActivity"
-            android:theme="@style/DolphinTvGamecube">
+            android:theme="@style/DolphinTvBase">
 
             <!-- This intentfilter marks this Activity as the one that gets launched from Home screen. -->
             <intent-filter>
@@ -55,12 +55,12 @@
 
         <activity
             android:name=".features.settings.ui.SettingsActivity"
-            android:theme="@style/DolphinSettingsGamecube"
+            android:theme="@style/DolphinSettingsBase"
             android:label="@string/preferences_settings"/>
 
         <activity
             android:name=".activities.EmulationActivity"
-            android:theme="@style/DolphinEmulationGamecube"/>
+            android:theme="@style/DolphinEmulationBase"/>
 
         <activity
             android:name=".activities.CustomFilePickerActivity"
@@ -81,7 +81,6 @@
             </intent-filter>
         </activity>
 
-
         <service android:name=".services.DirectoryInitializationService"/>
         <service android:name=".services.GameFileCacheService"/>
         <service