Revert "Exposes capture methods to AudioServer + documentation" #30468

Reverts the following commits:

- c81ec6f26d:
  "Exposes capture methods to AudioServer, variable renames for
  consistency, added documentation."
- 47c558b98a:
  "Expose audio callbacks as signals."
- dabaa11b3c:
  "Fix to make sure the capture buffers are deallocated at shutdown.
  Silences warnings."

Some documentation improvements were kept for pre-existing methods.

See rationale for reverting these changes in #30468.

servers/audio/audio_stream.h

@@ -123,7 +123,7 @@ class AudioStreamPlaybackMicrophone : public AudioStreamPlaybackResampled {
 	friend class AudioStreamMicrophone;
 
 	bool active;
-	unsigned int capture_ofs;
+	unsigned int input_ofs;
 
 	Ref<AudioStreamMicrophone> microphone;