Similar to gst_rtp_buffer_get_extension_data, but more suitable for language bindings usage.
bits will contain the extension 16 bits of custom data and the extension data (not including the extension header) is placed in a
new Bytes structure.
If this did not contain an extension, this function will return
unchanged. If there is an extension header but no extension data then an empty Bytes will
the RTP packet
location for header bits
A new Bytes if an extension header was present and