Squad

* ci: fix off-by-one error

* squad.run: exec an actual gunicorn process
* ci: handle maximum fetch attempts in works as well

* core: fix query for "test pass %"
* ci: limit fetch attempts with temporary issues
* ci/lava:
* Fix exception handling for failed log fetching
* disable log fetching for the moment

* core.admin: list and fiter by ProjectStatus.finished
* ci/lava:
* speed up parsing of structured logs and test results from YAML
* fix parsing of test suite names

**IMPORTANT:** starting from this version, the LAVA backend for CI jobs
requires that PyYAML has been compiled with support for libyaml. So if you are
upgrading from a previous version and are using the LAVA integration, make sure
that is the case.

* `python3 -c 'import yaml; print(yaml.__with_libyaml__)'` must print `True`
* if not, make sure you have the development files for libyaml installed
(e.g. `libyaml-dev`) _before_ (re)installing PyYAML.
* To reinstall PyYAML:
`pip install --upgrade --force-reinstall --no-cache-dir PyYAML`

* ci: Reimplement poll as a series of fetch operations
* core.queries: optimize query for "tests pass %" metric
* frontend: add links to test history

* ci:
* formally associate TestJobs with their target build
* lava: remove per-job failure notifications
* core/Build: use pending CI jobs in the definition of `finished`
* core/notification:
* add support for delayed notifications
* core/notification:
* drop retry logic from notification task
* extract a reusable base HTML template
* force sending notifications after a timeout
* improve design of moderation warning in HTML
* notify admins of failed test jobs
* frontend:
* add filtering to build page
* add floating table headers
* list failures on top, and allow filtering in Test results page
* prioritize test suites with failures in build page