feat: allow searching for specific package versions using matchspec

[simonjung1603]

solves #3173

I allowed specifying a MatchSpec for the exact search so that for example

• pixi search "rattler-build<=0.35.4"
• pixi search "rattler-build[build=h3ab7716_0]"

are valid search calls and yield the respective package versions.

I added the examples from the issue to the search_extender docs.
I added a test case in search_tests.rs for this feature.

[baszalmstra]

Very cool! This looks great! I left one small comment!

[trim21]

👀 any progress？

I can work on this is the author allow it

[ruben-arts]

@trim21 from our side you would be welcome to continue this work! If @simonjung1603 doesn't react I would recommend to fork his work and continue from there.

[simonjung1603]

@trim21 from our side you would be welcome to continue this work! If @simonjung1603 doesn't react I would recommend to fork his work and continue from there.

Hey, I am fine with either. I'd happily continue, frankly I wasn't sure how you wanted me to proceed as I didn't get a reply on my comment about wildcard matchspec and the error message. Sorry for not poking you to follow up but I was otherwise occupied.

@trim21 if you have enough changes planned and want to take over, you have my permission. Just let me know.

If all this needs to be merged is a rewording of the diagnostic though then I'd propose I finish it.

[trim21]

So looks like this is a communication things 🤔

[ruben-arts]

I'm so sorry, this is totally my fault, I lost track of this PR. I took the responsibility of testing and adjusting the PR so that it would be merge ready in my opinion.

@simonjung1603 Thanks for the work!