feat(global): direct .conda installation

[lucascolley]

This PR includes necessary fixes to make pixi global install --path /path/to/.conda work, across test cases for absolute paths and various forms of relative paths. It also adds an error message for passing path-like args to pixi global install without passing --path, with a helpful error message.

It also checks that pixi global update and pixi global sync seem to work correctly following such installations.

[lucascolley]

the first part of the test is passing for me locally, we just need to make it generic over platforms and copy what is necessary to the temporary directory for CI, I think.

For the second part of the test, if we want to disallow direct installation of .conda files without --path, we need to add some check to be hit from

pixi/crates/pixi_cli/src/global/global_specs.rs

Lines 116 to 125 in a15e2fa

	} else {
	self.specs
	.iter()
	.map(|spec_str| {
	pixi_global::project::GlobalSpec::try_from_str(spec_str, channel_config)
	.map_err(Box::new)
	.map_err(GlobalSpecsConversionError::FromMatchSpec)
	})
	.collect()
	}

.

---

I'll continue with this when Julian is back next week.

[Hofer-Julian]

Thanks, Lucas!