improvement: add `has_dep?/2` #772

Job	Run time
ash-ci / mix igniter.upgrade	0s
ash-ci / mix deps.get	22s
ash-ci / audit	58s
ash-ci / MIX_ENV=test mix.compile	41s
ash-ci / MIX_ENV=dev mix.compile	24s
ash-ci / mix credo --strict	7s
ash-ci / mix ash.codegen --check	0s
ash-ci / mix docs	1m 13s
ash-ci / mix dialyzer	2m 37s
ash-ci / Deploy docs to GitHub pages.	8s
ash-ci / mix format --check-formatted	1m 18s
ash-ci / mix sobelow	4s
ash-ci / mix spark.cheat_sheets --check	12s
ash-ci / mix spark.formatter --check	5s
ash-ci / mix test	1m 29s
ash-ci / mix deps.unlock --check-unused	40s
ash-ci / Release	0s
	10m 18s

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