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/src/main/java/com/github/damontecres/wholphin/mpv/MPVLib.kt

@@ -0,0 +1,26 @@
+package com.github.damontecres.wholphin.mpv
+
+/**
+ * Stubs out MPVLib in wholphin-mpv
+ */
+object MPVLib {
+    fun setPropertyString(
+        key: String,
+        value: String,
+    ): Unit = throw MpvStubException()
+
+    fun setPropertyInt(
+        key: String,
+        value: Int,
+    ): Unit = throw MpvStubException()
+
+    fun setPropertyDouble(
+        key: String,
+        value: Double,
+    ): Unit = throw MpvStubException()
+
+    fun setPropertyBoolean(
+        key: String,
+        value: Boolean,
+    ): Unit = throw MpvStubException()
+}

wholphin-mpv-stub/src/main/java/com/github/damontecres/wholphin/mpv/MpvPlayer.kt

@@ -0,0 +1,22 @@
+package com.github.damontecres.wholphin.mpv
+
+import android.content.Context
+import android.os.Looper
+import androidx.annotation.OptIn
+import androidx.media3.common.SimpleBasePlayer
+import androidx.media3.common.util.UnstableApi
+import kotlin.time.Duration
+
+/**
+ * Stubs out MpvPlayer in wholphin-mpv
+ */
+@OptIn(UnstableApi::class)
+class MpvPlayer(
+    private val context: Context,
+    private val enableHardwareDecoding: Boolean,
+    private val useGpuNext: Boolean,
+) : SimpleBasePlayer(Looper.getMainLooper()) {
+    override fun getState(): State = throw MpvStubException()
+
+    var subtitleDelay: Duration = throw MpvStubException()
+}

wholphin-mpv-stub/src/main/java/com/github/damontecres/wholphin/mpv/MpvStubException.kt

@@ -0,0 +1,3 @@
+package com.github.damontecres.wholphin.mpv
+
+class MpvStubException : Exception("This build is using wholphin-mpv-stub which does not implement actual functionality")