Decode one packed ternary plane with the shared ggml_cuda_dt3_get_trit
helper (shifts, masks and a small pow3 table; the uint8_t wrap-around of
the intermediate product is intentional and matches the CPU reference).
The qh bytes hold only 4 trits; their 5th base-3 digit is packing padding
that always decodes to -1 and is never read.
Wires DT3 into the generic dequantize_block templates (to fp32/fp16/bf16,
contiguous and not) and into get_rows, and enables GET_ROWS in
supports_op.
Millaguie
4dfb210207