Use conda-lock to create lock files

[nh13]

See: https://github.com/conda-incubator/conda-lock. We could then support multi-arch lock files.

Possible Implementation

The Solve command would have an option --conda-lock=<arch> that would run:

conda-lock lock -f <env-name>.yaml -p <arch> --lockfile <env-name>-conda-lock.yml
conda-lock render --kind explicit --filename-template <env-name>-<arch>.lock <env-name>-conda-lock.yml

The <env-name>-<arch>.lock would then be parsed so that the URL/hash given for conda packages is stored in the version string in the output YAML, while for pip packages, everything after the # pip <package-name> @.

Then Assemble would generate a <env>-<arch>.lock file instead of a <env>.yaml for <env-name>.build-conda.sh to use. The latter would use conda-lock install --name <env> <env>-<arch>.lock. Does Assemble know it's a conda-lock version if the "version" is a URL, or should we have an explicit option --conda-lock=<arch>? If the latter, must the architecture be encoded in the filename?

Note: both the conda-lock render and install commands use the --mamba option in conda-lock lock, so set those if --mamba given to conda-env-bulider

[nh13]

Alternatively, we could have Assemble create a lock file directly, which may be cleaner than having solve create the lock file and shoe horn it into the YAML.