Don't leak MediaFileHandle when downloading voice messages (#1748)

Uses the new `MediaFile.persist()` [API](https://github.com/matrix-org/matrix-rust-sdk/pull/2789) to cache voice messages.
This allows to close the `MediaFile` handle after use and keeping the file.
Also disables rust sdk caching for voice messages as we'll use the app's cache dir for that purpose.

Fixes: https://github.com/vector-im/element-meta/issues/2175

libraries/matrix/test/src/main/kotlin/io/element/android/libraries/matrix/test/media/FakeMediaFile.kt

@@ -17,11 +17,16 @@
 package io.element.android.libraries.matrix.test.media
 
 import io.element.android.libraries.matrix.api.media.MediaFile
+import java.io.File
 
 class FakeMediaFile(private val path: String) : MediaFile {
     override fun path(): String {
         return path
     }
 
+    override fun persist(path: String): Boolean {
+        return File(path()).renameTo(File(path))
+    }
+
     override fun close() = Unit
 }

libraries/matrix/test/src/main/kotlin/io/element/android/libraries/matrix/test/media/FakeMediaLoader.kt

@@ -42,7 +42,12 @@ class FakeMediaLoader : MatrixMediaLoader {
         }
     }
 
-    override suspend fun downloadMediaFile(source: MediaSource, mimeType: String?, body: String?): Result<MediaFile> = simulateLongTask {
+    override suspend fun downloadMediaFile(
+        source: MediaSource,
+        mimeType: String?,
+        body: String?,
+        useCache: Boolean,
+    ): Result<MediaFile> = simulateLongTask {
         if (shouldFail) {
             Result.failure(RuntimeException())
         } else {