Add dependency parsing grammar for gateway allowlist

[psschwei]

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Summary

Part of #369

This PR adds the dependency specification grammar from PEP 508 (https://peps.python.org/pep-0508/) to use when validating dependencies via the allowlist.

As a temporary measure, it also simplifies the check to only consider the dependency and not a specific version. As such, it has dropped the test for related to dependency version.

Future work should be done to convert the allowlist file from JSON to the standard requirements.txt format, which would allow for easier version checking.

Details and comments

[psschwei]

The gateway pod seems to be restarting in the k8s test, not sure why yet

[psschwei]

huh, it's getting hit with an OOMKilled error... that doesn't happen locally, could just be an issue in the action...

[psschwei]

ok, bumping the resource limits on the gateway fixed the issue

[Tansito]

Good to know because we had the same problem with the scheduler Wed 😂

[Tansito]

Add it on-hold tag until we can work together on this 😄