Remove input track descriptors, add async getters on tracks for everything, deprecate old sync getters

test/node/flac-encoder-extension.test.ts

@@ -66,9 +66,9 @@ test('FLAC encoding', async () => {
 	});
 
 	const track = (await input.getPrimaryAudioTrack())!;
-	expect(track.codec).toBe('flac');
-	expect(track.sampleRate).toBe(sampleRate);
-	expect(track.numberOfChannels).toBe(channels);
+	expect(await track.getCodec()).toBe('flac');
+	expect(await track.getSampleRate()).toBe(sampleRate);
+	expect(await track.getNumberOfChannels()).toBe(channels);
 
 	const sink = new EncodedPacketSink(track);
 	let packetCount = 0;