Remove package from base environment

[soapy1]

This PR implements the ability for conda-self to uninstall packages from the base environment. conda self will block uninstalling packages that are required. For example,

conda-self will block uninstalling conda

$ pixi run conda self remove conda                                                                                                                                                  

Package 'conda' can not be removed. Aborting!

conda-self will uninstall other requested packages

$ pixi run conda remove conda-declarative                                                                                                                                          
Channels:
 - defaults
Platform: linux-64
Collecting package metadata (repodata.json): done
Solving environment: done

## Package Plan ##

  environment location: /home/sophia/projects/conda-self/.pixi/envs/default

  removed specs:
    - conda-declarative


The following packages will be REMOVED:

  conda-declarative-0.0.0dev0-py_0
  tomli-2.0.1-py313h06a4308_1
  tomli-w-1.2.0-pyhd3eb1b0_0


Proceed ([y]/n)? y


Downloading and Extracting Packages:

Preparing transaction: done
Verifying transaction: done
Executing transaction: done

[jaimergp]

Same comment here as in #6 (comment)