Add envs.py for environment checks and update imports in test files

[xin3he]

Description

testing_utils is only used by tests and should be removed from main folder.

Type of Change

• Bug fix
• New feature
• Documentation update
• Performance improvement
• Code refactoring
• Other (please specify):

Related Issues

Fixes or relates to #1134

Checklist Before Submitting

• My code has been tested locally.
• Documentation has been updated as needed.
• New or updated tests are included where applicable.

[Copilot]

Pull request overview

This PR moves test-only environment/helpers utilities out of the main auto_round package surface by introducing a test-local envs module and updating CUDA/CPU tests to import environment gates (e.g., require_*, multi_card, has_module) from it instead of auto_round.testing_utils.

Changes:

• Replaced auto_round.testing_utils imports across CUDA and CPU test suites with ...envs relative imports.
• Standardized test dependencies on environment checks to be test-local (supporting removal of testing_utils from the main package).

Reviewed changes

Copilot reviewed 22 out of 23 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
test/test_cuda/schemes/test_auto_scheme.py	Switches multi_card import to test-local envs.
test/test_cuda/quantization/test_mxfp_nvfp.py	Switches require_awq/require_optimum imports to test-local envs.
test/test_cuda/quantization/test_mxfp_and_nvfp_quant.py	Switches has_module import to test-local envs.
test/test_cuda/quantization/test_mix_bits.py	Switches require_* imports to test-local envs.
test/test_cuda/quantization/test_2_3bits.py	Switches require_* imports to test-local envs.
test/test_cuda/models/test_vlms.py	Switches require_* imports to test-local envs.
test/test_cuda/models/test_support_vlms.py	Switches require_* imports to test-local envs.
test/test_cuda/models/test_diffusion.py	Switches require_* imports to test-local envs.
test/test_cuda/models/test_conv1d.py	Switches require_gptqmodel import to test-local envs.
test/test_cuda/integrations/test_transformers.py	Switches is_ipex_available import to test-local envs.
test/test_cuda/export/test_gguf.py	Switches require_gguf import to test-local envs.
test/test_cuda/export/test_export.py	Switches require_* imports to test-local envs.
test/test_cuda/export/test_auto_round_format.py	Switches require_* imports to test-local envs.
test/test_cuda/core/test_main_func.py	Switches require_* imports to test-local envs.
test/test_cuda/backends/test_triton_backend.py	Switches require_greater_than_050 import to test-local envs.
test/test_cuda/backends/test_torch_backend.py	Switches require_* imports to test-local envs.
test/test_cuda/backends/test_exllamav2_backend.py	Switches require_* imports to test-local envs.
test/test_cuda/advanced/test_multiple_card_calib.py	Switches multi_card import to test-local envs.
test/test_cuda/advanced/test_multiple_card.py	Switches multi_card/require_* imports to test-local envs.
test/test_cpu/quantization/test_mxfp_save_load.py	Switches has_module import to test-local envs.
test/test_cpu/quantization/test_mix_bits.py	Switches require_gptqmodel import to test-local envs.
test/test_cpu/backends/test_torch_backend.py	Switches require_* imports to test-local envs.