Glotter2

* Fix bug that would indicate "No tests were found" when filtering tests

* Remove call to `time.sleep` when pulling image

* Bump version since wrong version pushed to pypi

* Change test ID from `<filename>` to `<language>/<filename>`
* Speed up test collection by about 1 min and total test time by about
5 min in [sample-programs][sample-programs] by caching list of sources
* Modify `download`, `run`, and `test` commands so that `-p`, `-l`, and
`-s` are no longer mutually exclusive
* Add `--parallel` to `download` command to parallelize image downloads
* Add `--parallel` to `test` command to parallelize tests

* Fix crash when running tests for [sample-programs][sample-programs]
with glotter 0.2.x
* Upgrade dependencies to latest version:
* `docker >=6.0.1, <7`
* `Jinja >=3.1.2, <4`
* `pytest >=7.2.1, <8`
* `PyYAML >=6.0, <7`
* Upgrade python to 3.8 or above