SfpCodec::Dec2F and ComressTraits<T>::Decompress2 for all supported types. It also allows to remove one of the specializations of GEMM_4x4_Tile, handling compressed MatB with one function. As before even when MatA is bf16 it is using 32-bit registers for computations.
Measurements for a 2b-it sfp-encoded model on a AMD Ryzen Threadripper PRO 3945WX 12-Cores:
baseline:
```
32.6254 prefill tokens / sec
8.91429 tokens / sec
115 milliseconds time to first token
```
this change:
```
54.3045 prefill tokens / sec
16.8191 tokens / sec
56 milliseconds time to first token
```
PiperOrigin-RevId: 651369694
Jan Wassenberg
Andrey Vlasov
Austin Huang