chore: align `Headers` to spec (#10199)

This commit aligns `Headers` to spec. It also removes the now unused
03_dom_iterable.js file. We now pass all relevant `Headers` WPT. We do
not implement any sort of header filtering, as we are a server side
runtime.

This is likely not the most efficient implementation of `Headers` yet.
It is however spec compliant. Once all the APIs in the `HTTP` hot loop
are correct we can start optimizing them. It is likely that this commit
reduces bench throughput temporarily.

1 files changed, 0 insertions, 0 deletions

diff --git a/test_util/wpt b/test_util/wpt
-Subproject e19bdbe96243f2ba548c1fd01c0812d645ba0c6
+Subproject 579608584916d582d38d0159666aae9a6aaf07a