Always treat waveform as List<Float> (#1663)

[MSC3246](https://github.com/matrix-org/matrix-spec-proposals/pull/3246) specifies the waveform as a list of ints because:

> Because floating point numbers are not allowed in Matrix events

Though DSP on audio data is almost always done using their floating point representation.
This PR brings the float<->int rescaling in the `matrix` module so that the application code can always work with float waveform samples.

libraries/mediaupload/api/src/main/kotlin/io/element/android/libraries/mediaupload/api/MediaSender.kt

@@ -55,7 +55,7 @@ class MediaSender @Inject constructor(
     suspend fun sendVoiceMessage(
         uri: Uri,
         mimeType: String,
-        waveForm: List<Int>,
+        waveForm: List<Float>,
         progressCallback: ProgressCallback? = null
     ): Result<Unit> {
         return preProcessor

libraries/mediaupload/api/src/main/kotlin/io/element/android/libraries/mediaupload/api/MediaUploadInfo.kt

@@ -29,6 +29,6 @@ sealed interface MediaUploadInfo {
     data class Image(override val file: File, val imageInfo: ImageInfo, val thumbnailFile: File) : MediaUploadInfo
     data class Video(override val file: File, val videoInfo: VideoInfo, val thumbnailFile: File) : MediaUploadInfo
     data class Audio(override val file: File, val audioInfo: AudioInfo) : MediaUploadInfo
-    data class VoiceMessage(override val file: File, val audioInfo: AudioInfo, val waveform: List<Int>) : MediaUploadInfo
+    data class VoiceMessage(override val file: File, val audioInfo: AudioInfo, val waveform: List<Float>) : MediaUploadInfo
     data class AnyFile(override val file: File, val fileInfo: FileInfo) : MediaUploadInfo
 }