[Quant][fx] Refactor lowering code (part 1) (#74128)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/74128
**Summary:** This commit is the first step towards refactoring the
lowering code in _lower_to_native_backend.py. The main changes
included in this commit are:
(1) Remove the use of the subgraph rewriter in lowering
(2) Replace the use of `is_match` with manual pattern matching
The motivation behind (2) is it simplifies the lowering code
significantly; previously we had many different but similar
patterns for slightly different models. There should be no
change in behavior with this PR.
Note that this is only part 1 of the refactoring. Part 2
will merge the static and dynamic lowering code paths
and refactor the currently duplicate pattern matching /
cleanup code into common helper functions.
**Test Plan:**
python test/test_quantization.py TestQuantizeFx
python test/test_quantization.py TestQuantizeFxOps
**Reviewers:** jerryzh168
**Subscribers:** jerryzh168
Test Plan: Imported from OSS
Reviewed By: jerryzh168
Differential Revision: D34910597
Pulled By: andrewor14
fbshipit-source-id: c6fea0c538ce5efc5afaf53e072922528988dda7
(cherry picked from commit fa05cb9fc0909fe6e199a6b50ea2001c9e9ac0ee)
