Add partial generation from CMv2.9 & CMv4.0 XML

[quietvoid]

Needs more testing.
Only supports L1 and L2 trims.

For some reason L2 values from XML and RPUs are different for Netflix's Sparks.

Samples for L5 or other trims welcome.

[quietvoid]

If anyone wants to test, artifacts will be here: https://github.com/quietvoid/dovi_tool/actions/runs/1169155763
RPU can be generated using dovi_tool generate --xml metadata.xml

[quietvoid]

Most of the time, trim_slope (Gain) is different in the RPU vs the XML. The rest should be accurate.
New test build: https://github.com/quietvoid/dovi_tool/actions/runs/1169155763

[quietvoid]

Added CMv4.0 partial support. L1, L2 and L3 metadata are parsed.
I still don't know how L5 works, and L8 requires calculations to regenerate L2 so I don't really plan on supporting it.

L3 metadata might be wrong, not sure since I have nothing to compare against.

Still need to calculate L4 metadata from L1 & scene changes.

Build: https://github.com/quietvoid/dovi_tool/actions/runs/1169155763

[quietvoid]

Looks like L4 metadata relies on the picture itself (mean & stdev of [maxR, maxG, maxB] for every frame), so it can't be generated from XML.

[quietvoid]

I understand the concept, just not how the values in the XML correlate with a border offset.