inherit additional deps from an environment in `[edgetest.envs.core]`

[ryanSoley]

it'd be nice if I only had to specify my library's dependencies in [edgetest.envs.core] instead of needing to remember to add every new test dependency. there's already a considerable amount of env declaration duplication required throughout the various package managing tools, so it'd be nice if there wasn't another layer of duplication here

I'd like to only need to specify the libraries I want to try updating in [edgetest.envs.core]. I'd like to inherit the rest of the dependencies from an environment file. for example:

[edgetest.envs.core]
python_version = 3.9
conda_install = 
	./environment.yml
extras = 
	all
upgrade = 
	click
	dask[dataframe]
	fsspec
	intake[dataframe]
	pandas
	pyarrow
	PyYAML
	s3fs
	prefect
	dash
	dash-bootstrap-components

[ryanSoley]

for context, Shania has been adding new examples that get tested during our test suite. these examples can have a number of dependencies that aren't actual rubicon dependencies and we've been forgetting to add them to the edgetest config too, resulting in fails the next night

capitalone/rubicon-ml#222

it's certainly not a problem with edgetest - we just need to remember - but it'd be cool if we didn't need to remember

[fdosani]

@ryanSoley I'll circle around this when @ak-gupta is back from vacation. I think it would be nice to specify a file, could just be something like conda_install_yaml in addition to conda_install or something along those lines.