Rework CLI

[nscuro]

Overall, there are three ways in which SBOMs can be generated for Go projects:

1. Module based (go list -m, go mod why -m)
   • This is what we're currently doing
2. Application based (go list -deps ./cmd/myapp)
   • This is what has been discussed in Incorrect/Extra Data included in sbom. #20
3. Binary based (go version -m ./myapp.exe)
   • See Add support for creating SBOMs from binaries #21

The CLI should clearly separate these cases, especially since some options will not apply to all ways.
Which way is chosen should be an active decision, as each way has implications that users should be aware of.

Status

• app Add support for application SBOMs #50
• bin Generate SBOMs from binaries #46
• mod Introduce multi-command CLI #45
• version Introduce multi-command CLI #45