[quant][pt2e][improvement] Remove the need to annotate all nodes with default annotation (#99001)
Summary:
This PR changes prepare to use some default observer/fq constructor when "target_dtype_info" is not set, this allows user to not initialize all nodes to default
observer/fq constructor. Note we may still need to annotate intermediate node after this PR, there will be a follow up PR to allow users to only annotate things they
want to quantize
Test Plan:
python test/test_quantization.py TestQuantizePT2E
python test/test_quantization.py TestQuantizePT2EModels
Reviewers:
Subscribers:
Tasks:
Tags:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/99001
Approved by: https://github.com/kimishpatel, https://github.com/andrewor14
