[NNCF] Move is_weight_compression_needed and BackendParameters to com…

[Aryanpagaria]

###Summary

This PR refactors duplicated logic for weight compression handling across different backends.
The is_weight_compression_needed function and the BackendParameters class were previously defined in multiple backend-specific files (FX and OpenVINO).
Since the logic is identical, they have now been consolidated into a single shared module for better code reuse and maintainability.

###Changes Made

Moved common logic to a new file:
src/nncf/common/quantization/backend_parameters.py

Removed backend-specific duplicates:

src/nncf/experimental/torch/fx/quantization/backend_parameters.py

src/nncf/openvino/quantization/backend_parameters.py

Updated import statements in affected modules to reference the new common file.

No logic changes — purely a structural refactor.

###Reason for Change

Having identical logic across multiple backend implementations caused unnecessary duplication and made maintenance harder.
This refactor improves:

Code consistency

Readability

Ease of future modifications

###Testing

Ran full pytest suite — all tests passed successfully.

Verified that all backend compression logic functions as expected using the common implementation.

###Related Issue

Fixes: #3668

[ljaljushkin]

@Aryanpagaria thank you for the contribution!
Unfortunately, the #3668 issue was assigned to @aobolensk and there's a PR waiting for review: #3669
@daniil-lyakhov, will #3669 be merged?