Add AVX2 implementation of deblocking filter / port deblocking asm from HEVC

[stone-d-chen]

• Port as much for HEVC deblock asm to VVC code as possible
• Add VVC specific deblocking code

References

• VVC In Loop filters paper

[stone-d-chen]

Chroma Deblocking Notes

VVC has three types of Chroma deblocking filter operations:

• long-tap filter FUNC(loop_filter_chroma_strong)
• short-tap filter `FUNC(loop_filter_chroma_weak) (equivalent to the HEVC chroma deblocking)
• long-tap filter with reduced support FUNC(loop_filter_chroma_strong_one_side)

The filter choice depends on the CU/TU block side length (ortho to boundary being deblocked):

• Upper side of horizontal is restricted to ($S_p = 1$), otherwise
• if block side $\geq 8$ samples, then $Sp, Sq = 3$, otherwise
• $Sp, Sq = 1$

When $Sp = Sq = 1$ the short-tap (chroma_weak) is applied. This filter is identical to the (only) HEVC deblocking filter:

$$ \Delta_c = \left((q_0 - p_0 << 2) + p_1 - q_1 + 4\right) >> 3 $$

One general difficult with incremental implementation is that ff_vvc_deblock_horizontal calls a single function vvcdsp.lf.filter_chroma which implements the filter decision calculation -> filtering. If I can at least temporarily do some checks in ff_vvc_deblock_horizontal then I can call hevc's asm implementation directly.