Dedupliate syn (#33038)

This is the last step toward removing our use of `syn` version
1. It does three things:

1. Upgrades `async-recursion` to a newer version that uses `syn` 2.
2. Removes the use of `enum-iterator` that was only used to produce a
   trivial list of enum names. This reduces the number of crates we
   dependo on by 2.
3. Upgrades `media` to a version which no longer uses `syn` 1

Fixes #33034.

Signed-off-by: Martin Robinson <mrobinson@igalia.com>

components/net/Cargo.toml

@@ -14,7 +14,7 @@ test = false
 doctest = false
 
 [dependencies]
-async-recursion = "0.3.2"
+async-recursion = "1.1"
 async-tungstenite = { workspace = true }
 base = { workspace = true }
 base64 = { workspace = true }