Attempt to resolve conflicts with ENABLE_QPA_SUB_CTU but finally make it mutually exclusive with JVET_M0113_M0188_QG_SIZE (to be fixed later)

keep max TU in #define for possibility of keeping the parameter

TU max/min size are constants in the VVC draft. Reflecting this in the software.

AMVR (formely IMV) now has only one mode, which used to be mode #2
- remove SPS imv_mode parameter
- remove encoder configuration for mode #1 (mode #2 replaces mode #1)
- adapt config files to refer tp mode #1
- rename SPS syntax elements and access functions to AMVR

Note: IMV to AMVR renaming in other parts of the software should be done by proponents.

- all elements of SPSNext are moved into SPS
- syntax elements of SPS are sorted according to draft (as far as possible)
- comments were added where software and draft diverge

There is a conflict with JVET_M0427_INLOOP_RESHAPER that is triggering a debug assertion that checks that the width is not 1.