[quant] Fix per channel weight observer (#85883)
Summary: `per_channel_weight_observer_range_neg_127_to_127` now correctly uses `PerChannelMinMaxObserver` instead of `MinMaxObserver`
Test Plan:
Adds a new test `quantization.core.test_top_level_apis
` to instansiate and run `forward()` on all `default` observers
Differential Revision: D39916482
Pull Request resolved: https://github.com/pytorch/pytorch/pull/85883
Approved by: https://github.com/salilsdesai
