[action] [PR:18028] Move some SRv6 functions to srv6_helper.py (sonic-net#228)

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### Description of PR
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Summary: Move some SRv6 functions to srv6_helper.py
Fixes #
Move some SRv6 functions to `tests/common/helpers/srv6_helper.py`. If other features want to do integration testing with SRv6, they can call the function in `tests/common/helpers/srv6_helper.py` to prepare SRv6 environment.

### Type of change

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- [ ] Bug fix
- [ ] Testbed and Framework(new/improvement)
- [ ] New Test case
 - [ ] Skipped for non-supported platforms
- [x] Test case improvement

### Back port request
- [ ] 202012
- [ ] 202205
- [ ] 202305
- [ ] 202311
- [ ] 202405
- [ ] 202411

### Approach
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Author: mssonicbld