Code cleanup: fix variable names, use proper data types, etc.

See merge request jvet/VVCSoftware_VTM!2592

Avoid seg fault Slice::constructRefPicList

See merge request jvet/VVCSoftware_VTM!2593

When decoding a subset of temporal layers, it is possible that
inactive reference pictures may not be present in the DPB. In
such case a segmentation fault could be observed in
Slice::constructRefPicList. Marking of a picture as long term or
short term is changed to be skipped when a picture is missing.
An error is thrown when an active reference picture is missing.

JVET-AD0045: Encoder MV selections and DMVR revisited

See merge request jvet/VVCSoftware_VTM!2589

Fix #1597 nnpfc_constant_patch_size_flag and nnpfc_overlap and nnpfc_overlap parsing.

See merge request jvet/VVCSoftware_VTM!2586

Fix #1598: signal chroma location type when input is y4m

See merge request jvet/VVCSoftware_VTM!2588

JVET-AD0386: Processing Order SEI message update

See merge request jvet/VVCSoftware_VTM!2585

The default values of sps_chroma_horizontal_collocated_flag and
sps_chroma_vertical_collocated_flag are modified to take on values according to
the specified chroma location type. If no chroma location type is specified,
the default values of the flags are as prior to this commit.

JVET-AD0169: Downsampling filters in range 1.1 to 1.35 based on Kaiser(7) windowed sinc

See merge request jvet/VVCSoftware_VTM!2583

Fix #1599: include frame rate info in bitstream when provided in y4m file

See merge request jvet/VVCSoftware_VTM!2587

Express frame rate as ratio of two integer values throughout code
using struct Fraction

Add support for defining fractional frame rate from command line

Remove previous cycle macros

See merge request jvet/VVCSoftware_VTM!2584

Revert !2573 and add MultiLayerEnabledFlag=1 to two_layers.cfg

See merge request jvet/VVCSoftware_VTM!2582

Port changes from JVET-Z0072 to performance low delay configuration file

See merge request jvet/VVCSoftware_VTM!2577

Fixes for multilayer coding

See merge request jvet/VVCSoftware_VTM!2580