Add duration filters to test case search

[raydeveloperF]

Closes #1923

Summary

• add setup, testing, and expected duration filters to the /cases/search/ page
• initialize the existing duration picker widget on the search page and pass non-zero duration values into TestCase.filter
• make TestCase.filter normalize duration filter values and support filtering by annotated expected_duration

Testing

• LANG=en_US.UTF-8 .venv/bin/python manage.py test tcms.rpc.tests.test_testcase.TestCaseFilter tcms.testcases.tests.test_views.TestSearchCases --settings=tcms.settings.test -v2
• .venv/bin/flake8 tcms/rpc/api/testcase.py tcms/rpc/tests/test_testcase.py tcms/testcases/forms.py tcms/testcases/tests/test_views.py
• .venv/bin/black --check tcms/rpc/api/testcase.py tcms/rpc/tests/test_testcase.py tcms/testcases/forms.py tcms/testcases/tests/test_views.py
• .venv/bin/isort --check --diff tcms/rpc/api/testcase.py tcms/rpc/tests/test_testcase.py tcms/testcases/forms.py tcms/testcases/tests/test_views.py
• ./node_modules/.bin/eslint testcases/static/testcases/js/search.js
• git diff --check

[atodorov]

This appears to be related and/or somewhat duplicate of both
#2558 and #2530.

Can you explain what's the relationship between your code and these 2 previous contributions ?

If you are willing to work on this it should build on previous work and address comments already posted in previous pull requests, not start everything from scratch.