cmd/all, internal/all: migrate to cli v2

[jn-lp]

The second version of the library brought us many new methods, interfaces and structures. The main innovations are new props in the context structure, default values for boolean flags and the IsSet method for flags. Improved overall performance and reduced memory usage for applications.

Further reading

Release notes: https://github.com/urfave/cli/releases/tag/v2.0.0
Migration guide: https://github.com/urfave/cli/blob/master/docs/migrate-v1-to-v2.md

[holiman]

Thanks,
This PR will require extensive testing. It might be worth trying to put together testcases of expected flag combinations and their effects, to better evaluate this change, and verify that the CLI interface remains unchanged (or at least have documentation on what parts changed). I'll think about how to best test this.

[holiman]

This PR is a bit bitrotted, so we'll probably just go with #24751 instead. Sorry, and thanks for the effort!