[PT2][Quant] Introduce composable quantizer (#102846)
Summary:
Using composable quantizer, we can now composable two or more quantizers. In
the test here we compose quantizer configured with dynamic linear quantization,
with quantizer configured for static quantization.
Note that composable quantizer has strict order in which annotations are
applied
Test Plan: test_composable_quantizer*
Reviewed By: jerryzh168
Differential Revision: D46267690
Pull Request resolved: https://github.com/pytorch/pytorch/pull/102846
Approved by: https://github.com/andrewor14
