LibAudio: Split Buffer.{h, cpp} into three files

The Buffer files had contained both the ResampleHelper and the
sample format utilities. Because the Buffer class (and its file) is
going to be deleted soon, this commit separates those two things into
their own files.

Userland/Libraries/LibAudio/SampleFormats.h

@@ -0,0 +1,27 @@
+/*
+ * Copyright (c) 2022, kleines Filmröllchen <filmroellchen@serenityos.org>.
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/String.h>
+#include <AK/Types.h>
+
+namespace Audio {
+
+// Supported PCM sample formats.
+enum PcmSampleFormat : u8 {
+    Uint8,
+    Int16,
+    Int24,
+    Int32,
+    Float32,
+    Float64,
+};
+
+// Most of the read code only cares about how many bits to read or write
+u16 pcm_bits_per_sample(PcmSampleFormat format);
+String sample_format_name(PcmSampleFormat format);
+}