[modular] Decouple clap_generate from the builder API

Issue by epage Tuesday Oct 19, 2021 at 15:36 GMT Originally opened as https://github.com/clap-rs/clap/issues/2912

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[X] I have searched the discussions
[X] I have searched the existing issues

Clap Version

master

Describe your use case

We are looking to modular clap

We can look for opportunities to shrink clap
We can share logic with other argument parsers

One aspect of this will be to have a general reflection API. A good stepping stone test case is for clap_generate to not depend on clap but a clap_reflect.

Describe the solution you'd like

clap_generate to not depend on clap but a clap_reflect.

Alternatives, if applicable

No response

Additional Context