d3d12: Perf improvements

Significant perf improvements:

• Using a dynarray to track pending_barrier_bos
• Using a context-level array of dxil_wrap_sampler_state for filling shader keys, significantly reducing the size of the d3d12_shader_key. When a new variant is created, a new array for them is allocated, and the contents are copied over.
• Using a local array of batch_bo_reference_state to track up to 16 contexts worth of batches in d3d12_bo, effectively avoiding the use of a hash_table for the same purpose (while keeping the hash table around for >16 active context scenarios)
• Reducing calls to and cost of validate_geometry_shader_variant

Less significant perf improvements: Shader key compare and hash updates, not recomputing manual_depth_range in every shader variant selection, and unrolling the shader variant selection loop.