check: another pile of assert->X265_CHECK conversions
check: fix MSVC warnings and check behavior
check: disable MSVC warnings about constant conditionals with checked builds
checked: enable check macros in debug builds
cli: remove default strings for preset and tune, modify default AQ mode to match

The cli has used --tune ssim as the default since we've had an ssim tune, but
API users were getting the default aq-mode of 1 instead.  This commit removes
the default tune (and preset) strings and fixes the default param structure to
match the previous CLI default behavior (aq-mode 2)
api: introduce x265_encoder_parameters(), copy param earlier to avoid mods

in x265_encoder_open(), make a copy of the provided param structure much earlier
to avoid making any changes to the param strucutre provided by the user, in
case they want to use that same param again to allocate another encoder.
cutree: adjust the rowSatd with qpoffset only for reference frames
cutree: removed logLevel check from if loop
adapt psy-rd from x264

In this initial implementation, we only use sa8d to estimate the energy of the
source and reconstructed blocks. psy-rd is disabled by default, to evaluate use
--preset veryslow --psy-rd 1.0