fix: try to increase rlimit

[baszalmstra]

This is an attempt to fix #1551

This PR does two things:

• Concurrent prefix installations share the same io concurrency limit to ensure we dont open too many files when running multiple installations concurrently.
• Pixi attempts to increase the soft rlimit to a "more sensible" value of 1024.

@wolfv, @ruben-arts Would you be able to test this PR locally. I added a bunch of tracing to the rlimit setting. I wonder what happens on your machine.

[ruben-arts]

If I set the ulimit to 100 manually It tells me that it tried to overwrite it:

> ulimit -n 100

> pixi install
...
 INFO pixi::rlimit: Attempted to set RLIMIT_NOFILE to 1024 but was only able to set it to 100
...

Not sure if that would be expected but it at least keeps working for me.

[baszalmstra]

Mm since Im a Windows kinda guy Im not entirely sure how this is supposed to work. @wolfv Maybe you can help me out here.

Do you always see that info statement @ruben-arts ? Or did you have to use -v? It should not appear if you dont use -v.

[wolfv]

let me try with the large environment once again! :)

[wolfv]

Looks good! Old pixi version was consistently failing on ros2-nav2, but the build of this PR works like a charm! :)

[baszalmstra]

If you run the command with -v does it also tell you something about the rlimit?

[wolfv]

Yes! Similar to Ruben I got something like CB 1024