priority: add a test helper to override the init timeout in tests

[easwars]

This is an initial cleanup before the actual work required for #8516

The way the init timeout is currently overridden in existing tests is unnecessary complicated and hard to read. This simplifies things and ensures that the previous pattern is not followed when new tests are written.

RELEASE NOTES: none

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.24%. Comparing base (e816736) to head (0ee723f).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #8704      +/-   ##
==========================================
- Coverage   83.29%   83.24%   -0.05%     
==========================================
  Files         416      416              
  Lines       32267    32267              
==========================================
- Hits        26876    26862      -14     
- Misses       4017     4024       +7     
- Partials     1374     1381       +7     

see 19 files with indirect coverage changes

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[mbissa]

LGTM.