Update wholphin-extensions with newer MpvPlayer (#1365)

## Description
Uses the newer version of `wholphin-extensions` which now has the Kotlin
code, so this PR removes the MPV Kotlin code from this repo. Also
updates gradle to use providers.

There are no user facing changes

### Dev notes

`wholphin-mpv` can be provided by:
1. [Fetching pre-built
binaries](https://github.com/damontecres/wholphin-extensions#pre-built-binaries)
(Preferred method for devs)
2. Building `wholphin-extensions` from
[source](https://github.com/damontecres/wholphin-extensions#build-from-source)
3. Using `wholphin-mpv-stub` (the new module added in this PR) which
allows for compiling Wholphin, but will throw exceptions if MPV is used
during runtime

### Related issues
Related to #1172 

### Testing
Emulator

## Screenshots
N/A

## AI or LLM usage
None

wholphin-mpv-stub/build.gradle.kts

@@ -0,0 +1,38 @@
+plugins {
+    alias(libs.plugins.android.library)
+}
+
+android {
+    namespace = "com.github.damontecres.wholphin.mpv"
+    compileSdk {
+        version = release(36)
+    }
+
+    defaultConfig {
+        minSdk = 23
+
+        testInstrumentationRunner = "androidx.test.runner.AndroidJUnitRunner"
+        consumerProguardFiles("consumer-rules.pro")
+    }
+
+    buildTypes {
+        release {
+            isMinifyEnabled = false
+            proguardFiles(
+                getDefaultProguardFile("proguard-android-optimize.txt"),
+                "proguard-rules.pro",
+            )
+        }
+    }
+    compileOptions {
+        sourceCompatibility = JavaVersion.VERSION_11
+        targetCompatibility = JavaVersion.VERSION_11
+    }
+}
+
+dependencies {
+    implementation(libs.androidx.media3.exoplayer)
+    testImplementation(libs.junit)
+    androidTestImplementation(libs.androidx.junit)
+    androidTestImplementation(libs.androidx.espresso.core)
+}