Split common and weights into separate lib
Remove common-inl (does not have to be SIMD code), activations.cc
Centralize switch(Model) to avoid duplication
Move CompressWeightsT to compress_weights.cc
Move LoadWeights to weights.cc
PiperOrigin-RevId: 640869202
We only used inner_pool in the prefill FFW function, and there we
can achieve sufficient parallelism on the rows of the matrix-vector
multiplications.
Benchmark results on a 1600-token summarization task:
```
Prefill speed
Num threads BEFORE AFTER
4 9.24 t/s 9.76 t/s
18 31.41 t/s 31.16 t/s
32 31.41 t/s 45.13 t/s
64 31.03 t/s 57.85 t/s
```
Jan Wassenberg
Zelalem Aweke
Apoorv Reddy
Zoltan Szabadka