script: Implement parsing of Link HTTP headers (#39052)

The Link HTTP header can do the same as link elements,
in that they can preload/prefetch/etc... This implements
the basics of header parsing and hooks it up for preload.

Note that we use a new nom-rfc8288 crate that implements
the parsing behavior. However, that crate is too strict
in that empty attributes (;; as part of the header) are
discarded and resulting in a parsing failure. Therefore,
we use its lenient parsing mode.

Part of #35035

---------

Signed-off-by: Tim van der Lippe <tvanderlippe@gmail.com>
Signed-off-by: Tim van der Lippe <TimvdLippe@users.noreply.github.com>
Co-authored-by: Josh Matthews <josh@joshmatthews.net>

Cargo.toml

@@ -105,6 +105,7 @@ mozangle = "0.5.3"
 net_traits = { path = "components/shared/net" }
 nix = "0.30"
 nom = "8.0.0"
+nom-rfc8288 = "0.4.0"
 num-traits = "0.2"
 num_cpus = "1.17.0"
 openxr = "0.19"