[ENH] - Add ability to build env from lockfile

[kcpevey]

Feature description

I'd like the ability to create an env from a lockfile.

Value and/or benefit

Currently there is no way to truly reproduce an existing environment in conda-store. The closest we have is the exported, pinned environment.yml. A better option would be to allow conda lock files to be used to build envs. We give the lockfiles to the users, but we don't have a mechanism to ingest them.

The backend was recently updated to allow this (https://github.com/conda-incubator/conda-store/issues/676 and https://github.com/conda-incubator/conda-store/pull/772). Now the frontend will need work to enable users to use this new feature.

Anything else?

Things to consider:

• We will need a UI mechanism to accept the lockfile. I imagine the GUI/YAML toggle might need a third option of lock file so that it can have its own screen with a file browser widget and a viewer window? Designers may have better ideas.
• I'm not sure how the rest of the UI works, but we may need to sort out translation between lockfile back to the editable environment.yml. Just using the pinned conda export could be a solution for that once the env is built.

[trallard]

@gabalafou is currently working on this