Please separate CLI part of types loading (that uses yargs) from actual proto loading code

[koteisaev]

Is your feature request related to a problem? Please describe.

If the packages dependency tree contains the @grpc/proto-loader, as it happens with google-gax, it pulls with that a lot of code related to command line processing, such as yargs package and all its 40+ packages from dependencies.

Describe the solution you'd like

Most likely solution would be to separate the cli-specific functionality and its specific dependencies into something like @grpc/proto-loader-cli and use it via npx when necessary.

Describe alternatives you've considered

There is no way for me to do an alternative as this is a deep dependency of packages I use, such as @google-cloud/datastore which refers the google-gax which refers the @grpc/proto-loader surely without CLI-specific processing but for API calls using paths to proto files known by calling code.

Additional context

This will allow to get rid of dozens of dependencies which never called even indirectly in normal usage scenario of google-gax library (via Google Cloud client libraries and alike).