Consider reinstating CLI install command

[philwebb]

The CLI used to support spring install but we removed it as part of #32263. We might want to reconsider if we should support it.

[philwebb]

We discussed this today and we aren't planning to reintroduce the command. Restoring it will involve adding Maven libraries back into the CLI which we don't want to do. We also feel like our development time is currently best spent on core Spring Boot features which are likely to benefit more people.