feat: global update should add new executables

[nichmor]

This PR aims to change how pixi global update picks up and exposes new binaries.

• If the user initially chooses to auto-exposed everything, after the update we will remove binaries that are not anymore present and will expose the new ones. A good example of this could be python upgrade - we will remove python3.8 and will add python.39
• If the user initially exposed only a small subset of binaries, we will not auto-expose the new ones.

• adding python 3.8 and then modifying it manually to >=3.8, <3.10 as spec will result in this output

[Hofer-Julian]

Only a review of the code, since I didn't test it locally yet. I added a few comments.

In the description of this PR, you outlined quite nicely how the new behavior works. Could you please also do that in the docstring of the command?

[Hofer-Julian]

Same here

[nichmor]

^ here I think it will not work because I need to check if a name is in this exposed list. Changed it to hashset though ( instead of vec )

[Hofer-Julian]

I've now tested it locally and it works fine.

The tests on Windows are failing though.