DSC corrections

See merge request jvet/VVCSoftware_VTM!2807

Documentation contains instructions how to create keys. An untrusted key can be easily created by the user.

Specification requires initialization with bits equal to "1"

Due to the processing order of the decoder, NAL units always need to be stored, because the decoder
does not know yet, whether DSCI has arrived.

Also contains small fixed in error messages.

SEI related cleanups

See merge request jvet/VVCSoftware_VTM!2804

JVET-AJ0234: Allow for patch-wise operation when using spatial extrapolation

See merge request jvet/VVCSoftware_VTM!2800

JVET-AJ0128: Adding functionality to po_processing_degree_flag[i] of the SPO SEI message

See merge request jvet/VVCSoftware_VTM!2801

Fix for decoder when DSC SEI is not present

See merge request jvet/VVCSoftware_VTM!2802

JVET-AJ0131: Add nnpfc_inband_prompt_flag to gate NNPF text prompt

See merge request jvet/VVCSoftware_VTM!2798

fix ScalingList for multilayer, when used for only one layer that is not the...

See merge request jvet/VVCSoftware_VTM!2797

JVET-AJ0151: Digitally Signed Content SEI messages

See merge request jvet/VVCSoftware_VTM!2799

Ported from JVET-TuC with small improvements on certificate handling

Port ET with millisecond precision (from ECM MR 803)

See merge request jvet/VVCSoftware_VTM!2795

JVET-AJ0063: Proposal 1,2,4,5

See merge request jvet/VVCSoftware_VTM!2796