feat: add `pixi clean` command

[ruben-arts]

Initial proposal Includes

• pixi clean cleans environments
• pixi clean -e prod cleans a environment
• pixi clean cache cleans cache dir
• pixi clean cache --conda/--pypi cleans a specific package cache

fixes: #1321

[ruben-arts]

I'm not happy with the cli yet. I want env to be the default and cache being a sub command.

Edit: fixed

[bollwyvl]

pixi clean task <taskname> would also be very helpful.

In some systems (e.g. doit), clean can be optionally configured to remove:

• remove all outputs
  • clean = true
• some specific set of files
  • clean = ["*.tsbuildinfo", "lib"]
• the clean of all depends-on
  • clean-depends-on = true
    • though maybe this would be better when a depends-on can be a more full task with
      • depends-on = [{task="build", environment="build", clean=true}]

[ruben-arts]

@bollwyvl I like this idea!

[ruben-arts]

@bollwyvl I gave task a try but got burned out by the complexity of the glob work. Still think it's a good idea but I want to get the simple version in first.