fix(venv.relocatable): script entrypoints should work if symlinked to (#8079)

Fixes: #8058

## Test Plan

Integration test (but only for Unix, because symlinks on Windows require
admin privs. Plus, they are not really all that idiomatic on Windows)

crates/uv-virtualenv/src/virtualenv.rs

@@ -298,9 +298,7 @@ pub(crate) fn create(
 
         let virtual_env_dir = match (relocatable, name.to_owned()) {
             (true, "activate") => {
-                // Extremely verbose, but should cover all major POSIX shells,
-                // as well as platforms where `readlink` does not implement `-f`.
-                r#"'"$(dirname -- "$(CDPATH= cd -- "$(dirname -- "$SCRIPT_PATH")" > /dev/null && echo "$PWD")")"'"#
+                r#"'"$(dirname -- "$(dirname -- "$(realpath -- "$SCRIPT_PATH")")")"'"#
             }
             (true, "activate.bat") => r"%~dp0..",
             (true, "activate.fish") => {