DTIN-4234: Cleanup tox lint target

[jmakar-s1]

• Updated cryptography requirement to recent version in tox.ini
• Flake8, pylint lint fixes for a handful of files
• Updated scripts/verify-add-events-api-response-headers.py
• Moved docs from docs/monitors/kubernetes_monitor.md to scalyr_agent/builtin_monitors/kubernetes_monitor.py docs/monitors is generated with tox -e generate-monitor-docs

[github-actions[bot]]

Test Results

     20 files  +2       20 suites  +2   31m 49s :stopwatch: +19s 1 485 tests  - 3  1 465 :heavy_check_mark:  -   2    20 :zzz: ±0  0 :x:  - 1  7 096 runs   - 9  6 871 :heavy_check_mark:  - 10  225 :zzz: +2  0 :x:  - 1 

Results for commit d3d82747. ± Comparison against base commit 76e3704c.

This pull request removes 3 tests.

``` tests.unit.builtin_monitors.container_checker_test.ContainerCheckerFilterLabelsTest ‑ test_included_labels tests.unit.builtin_monitors.container_checker_test.ContainerCheckerMultiAccountTest ‑ test_check_containers_with_api_key_annotations tests.unit.builtin_monitors.container_checker_test.ContainerCheckerMultiAccountTest ‑ test_check_namespace_change ```

:recycle: This comment has been updated with latest results.