Use stable environments for remote and stdin scripts (#11364)

## Summary

This is a follow-on to #11347 to use a stable directory for remote and
stdin scripts. The annoying piece here was figuring out what to use as
the cache key. For remote scripts, I'm using the URL; for stdin scripts,
there isn't any identifying information, so I'm just using a hash of the
metadata.

crates/uv-python/src/environment.rs

@@ -1,10 +1,12 @@
-use owo_colors::OwoColorize;
 use std::borrow::Cow;
 use std::env;
 use std::fmt;
 use std::path::{Path, PathBuf};
 use std::sync::Arc;
+
+use owo_colors::OwoColorize;
 use tracing::debug;
+
 use uv_cache::Cache;
 use uv_cache_key::cache_digest;
 use uv_fs::{LockedFile, Simplified};