Reland "Structured Headers: Include all public tests"

This reverts commit 3cb9d56a.

Reason for revert: Removing extra-long tests from the test suite to get
the compile time down to something reasonable.

Original change's description:
> Revert "Structured Headers: Include all public tests"
> 
> This reverts commit 068d6078.
> 
> Reason for revert: Causes compile to hang for https://ci.chromium.org/p/chromium/builders/ci/Mac%20ASan%2064%20Builder
> 
> Original change's description:
> > Structured Headers: Include all public tests
> > 
> > This imports all of the tests from the public test repository at
> > https://github.com/httpwg/structured-header-tests, which have been
> > automatically converted from JSON to C++ unit tests.
> > 
> > Tests which were already present in structured_headers_unittest.cc
> > have been removed from that file, to avoid needless redundancy.
> > 
> > Bug: 1069790
> > Change-Id: I05536c36cb66c7dda43aab2f6c5ae77961120a6a
> > Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2146237
> > Commit-Queue: Ian Clelland <iclelland@chromium.org>
> > Reviewed-by: Asanka Herath <asanka@chromium.org>
> > Cr-Commit-Position: refs/heads/master@{#759015}
> 
> TBR=iclelland@chromium.org,asanka@chromium.org
> 
> # Not skipping CQ checks because original CL landed > 1 day ago.
> 
> Bug: 1069790
> Change-Id: I398e00aaa9903872475f8c5cb5f2513f99e38b69
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2159370
> Reviewed-by: Garrett Beaty <gbeaty@chromium.org>
> Commit-Queue: Garrett Beaty <gbeaty@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#761024}

TBR=iclelland@chromium.org,asanka@chromium.org,gbeaty@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 1069790
Change-Id: Ia0a66c1a864c40df637c3d0b18b864a4effad844
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2161414Reviewed-by: Ian Clelland <iclelland@chromium.org>
Reviewed-by: Asanka Herath <asanka@chromium.org>
Reviewed-by: Garrett Beaty <gbeaty@chromium.org>
Commit-Queue: Ian Clelland <iclelland@chromium.org>
Cr-Commit-Position: refs/heads/master@{#762486}

net/BUILD.gn

@@ -4289,6 +4289,7 @@ test("net_unittests") {
     "http/http_vary_data_unittest.cc",
     "http/mock_allow_http_auth_preferences.cc",
     "http/mock_allow_http_auth_preferences.h",
+    "http/structured_headers_generated_unittest.cc",
     "http/structured_headers_unittest.cc",
     "http/transport_security_persister_unittest.cc",
     "http/transport_security_state_unittest.cc",