codecs: h265: Don't process SPS when parsing codec_data.
gst_h265_decoder_parse_sps(), internally, executes gst_h265_decoder_process_sps(), which might call the new_sequence vmethod, which normally will negotiate downstream.
But gst_h265_decoder_parse_sps() is used also at gst_h265_decoder_parse_codec_data(), called when upstream negotiation is carried on, but processing the SPS will negotiate downstream without having set decoder's sink caps. This logic will skip the HDR metadata forwarding in video decoder base class, among other potential issues.
This patch adds a boolean parameters to gst_h265_decoder_parse_sps() to specify if the code wants to process the SPS or just to validate it.