Improve HTTP redirect following (#1637)

This implements HTTP redirect following ourselves.

The goal is:

1. All I/O is checked against `--allowed-resources` and
`--allowed-modules`, including HTTP redirects
2. HTTP rewrite rules can affect redirect following
3. HTTP headers can affect redirect following

---------

Co-authored-by: Islon Scherer <islonscherer@gmail.com>

stdlib/EvaluatorSettings.pkl

@@ -237,7 +237,7 @@ class Http {
   /// In the following example, an original request for `https://pkg.pkl-lang.org/my/pkg@1.0.0` is
   /// replaced with `https://my.internal.mirror/my/pkg@1.0.0`.
   ///
-  /// This does not affect `3XX` status code redirect following.
+  /// This also affects `3XX` status code redirect following.
   ///
   /// Example:
   ///