Use correct scope when parametrizing tests based on duts/asics

[vcheketx]

Description of PR

Summary:
Fixes parametrization based on duts/asics occuring per collected test instead of once per module

Type of change

• Bug fix
• Testbed and Framework(new/improvement)
• Test case(new/improvement)

Back port request

• 201911

Approach

What is the motivation for this PR?

Currently we are using enum fixtures for parametrization based on available duts/asics (e.g. enum_dut_hostname, enum_frontend_asic_index). These fixtures are parametrized inside pytest_generate_tests function using metafunc.parametrize with scope='module'.
If any test already has parametrization using @pytest.mark.parametrize, these enum fixtures will be recreated for each collected test, ignoring above mentioned scope.
This behavior can be easily noticed during copp/test_copp.py. Even on testbed with single DUT, examining setup/teardown during test shows that enum_rand_one_per_hwsku_frontend_hostname is recreated after each pair of tests, triggering teardown/setup of dependent fixtures. This adds ~40 minutes to test_copp.py execution time.

How did you do it?

Added override for enum fixtures outside of pytest_generate_tests with correct scope.

How did you verify/test it?

Run copp/test_copp.py - execution time decreased from ~55 minutes to ~15 minutes.

Note: tested only on single-DUT testbed.

Any platform specific information?

Supported testbed topology if it's a new test case?

Documentation

[abdosi]

LGTM. Verified