Update base for Update on "Add generic fake quantized linear for QAT"

**Summary:** This commit adds a generic fake quantized linear module
to replace the uses of the existing more specific QAT linears.
For example, `Int8DynActInt4WeightQATLinear` can be expressed
as follows:

```
from torchao.quantization.prototype.qat.api import FakeQuantizeConfig
from torchao.quantization.prototype.qat.linear import FakeQuantizedLinear

activation_config = FakeQuantizeConfig(torch.int8, "per_token", is_symmetric=False)
weight_config = FakeQuantizeConfig(torch.int4, group_size=8)
fq_linear = FakeQuantizedLinear(16, 32, False, activation_config, weight_config)
```

The main motivation is to provide a more flexible way to perform
QAT on models with linear layers. Previously, we would have to
create a new linear class every time we wish to experiment with
different fake quantization settings, e.g. different group size
or different bit width. Now we can express this easily using a
single linear module.

**Test Plan:**
python test/quantization/test_qat.py -k test_fake_quantize_config_granularity
python test/quantization/test_qat.py -k test_fake_quantize_config_granularity_error_cases
python test/quantization/test_qat.py -k test_fake_quantize_config_mapping_type
python test/quantization/test_qat.py -k test_fake_quantized_linear_8da4w
python test/quantization/test_qat.py -k test_fake_quantized_linear_4w

[ghstack-poisoned]

Author: andrewor14