entropy: remove m_ prefix from ContextModel.state, other nits
asm: cleanup unused sub_ps and add_ps

sub_ps and add_ps are used by CU or TU level, not PU level.
rc: set rdlevel to 2 in fast first pass for multipass encode.

increases speed of the first pass by over 70% in the slower presets with almost the
same quality in the final pass.
analysis: cleanup
quant: avoid runtime check of transform shift size
frameencoder: avoid redundant calls to resetEntropy()

All of the entropy coders need to be reset to the same state at the start of
the frame's analysis.  There is no point in re-calculating this initial state
repeatedly for each row
frameencoder: nit
entropy: disable signaling of CABAC init state

This flag, which was already disabled when frame parallelism is in use (which
is nearly always) was of limited utility. It did not improve compression
efficiency by any measurable amount, and it was expensive to compute.  But the
quality which made it expendable was that it was the only user of the bBinsCoded
flag in the ContextModel; forcing us to copy twice as much data every time we
copy a context.

With this feature removed, the context model can be reduced to a single uint8_t
state variable.
entropy: remove bBinsCoded from ContextModel (no more users)
entropy: remove ContextModel structure, use uint8_t directly
entropy: pad size of context array to 32 * 5 bytes
entropy: remove implicit memset from constructor

Before we do further refactors, we want Entropy instances allocated on the
stack to not perform any needless initialization work
main10: create a hybrid all-angs primitve for 16bpp compiles

The all-angs primitive is highly optimized assembly code that avoids a lot of
redundant work.  The all-angs C ref is horribly slow, doing redundant work to
mimic the output of the all-angs assembly code. Since we have no high bit depth
assembly for these functions, we'll use a shim C function that works very
similar to the C ref but it at least uses optimized primitives.

intra_allangs4x4	3.64x 	 6619.54  	 24097.30
intra_allangs8x8	5.66x 	 13722.49 	 77694.97
intra_allangs32x32	4.57x 	 246943.81 	 1129159.50

before:
encoded 1253 frames in 104.37s (12.01 fps), 366.08 kb/s, SSIM Mean Y: 0.9889624 (19.571 dB)

after:
encoded 1253 frames in 95.62s (13.10 fps), 366.08 kb/s, SSIM Mean Y: 0.9889624 (19.571 dB)
denoise: fix numCoeff (bug from 42b1d7c17510)
asm: cvt16to32_shr[*] for TSkip
asm: cvt32to16_shl[*] for TSkip