test_radv_ipv6_ra is unnecessarily skipped on non-dualtor topology

[wangxin]

Description of PR

Summary:
Fixes # (issue)

Type of change

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

Back port request

• 201911
• 202012
• 202205

Approach

What is the motivation for this PR?

Script test_radv_ipv6_ra.py is unnecessarily skipped on non-dualtor topology. The reason is that this script uses fixture toggle_all_simulator_ports_to_upper_tor which depends on cable_type fixture.

The cable_type fixture requires that the topology must has "dualtor", otherwise skip the test.

How did you do it?

This change updated the test_radv_ipv6_ra.py to use fixture toggle_all_simulator_ports_to_random_side.

How did you verify/test it?

Any platform specific information?

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

Documentation

[lolyu]

test_radv_ipv6.py uses fixture toggle_all_simulator_ports_to_upper_tor to do the mux toggle, which depends on cable_type. Actually, toggle_all_simulator_ports_to_upper_tor is designed for dualtor-io testcases. For normal t0 testcases, the practice is using fixture toggle_all_simulator_ports_to_random_side and choosing the random ToR as the testing device.
Suggest use toggle_all_simulator_ports_to_random_side instead.

[mssonicbld]

The pre-commit check detected issues in the files touched by this pull request.
The pre-commit check is a mandatory check, please fix detected issues.

Detailed pre-commit check results:
trim trailing whitespace.................................................Passed
fix end of files.........................................................Passed
check yaml...........................................(no files to check)Skipped
check for added large files..............................................Passed
check python ast.........................................................Passed
flake8...................................................................Failed
- hook id: flake8
- exit code: 1

tests/radv/test_radv_ipv6_ra.py:119:5: E125 continuation line with same indent as next logical line
tests/radv/test_radv_ipv6_ra.py:145:5: E125 continuation line with same indent as next logical line
tests/radv/test_radv_ipv6_ra.py:172:5: E125 continuation line with same indent as next logical line
tests/radv/test_radv_ipv6_ra.py:198:5: E125 continuation line with same indent as next logical line

check conditional mark sort..........................(no files to check)Skipped

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[mssonicbld]

@wangxin PR conflicts with 202205 branch

[mssonicbld]

Cherry-pick PR to 202305: #9299