Use atomic writes for the cache consistently (#546)

Ensure we're using atomic writes everywhere in our cache to avoid broken
cache records and error with parallel puffin actions
(https://github.com/astral-sh/puffin/pull/544#issuecomment-1838841581).

All json files that are written to the cache are written atomically and
the build wheels are written to temp dir and then moved atomically. I
didn't touch venv creation though, i don't think that's worth it since
python does not support atomic package installation through its design.

crates/puffin-cli/src/commands/venv.rs

@@ -88,10 +88,6 @@ fn venv_impl(
     )
     .into_diagnostic()?;
 
-    // If the path already exists, remove it.
-    fs::remove_file(path).ok();
-    fs::remove_dir_all(path).ok();
-
     writeln!(
         printer,
         "Creating virtual environment at: {}",