Conformance tests for static Gateway addresses

[shaneutt]

What type of PR is this?

/area conformance
/kind test

What this PR does / why we need it:

Going into GA we have an extended field for supplying static addresses for Gateways, but no conformance tests for that feature. This patch adds the test, while also tweaking some of the related condition reasons (see the explanation in the CHANGELOG.md).

Which issue(s) this PR fixes:

Resolves #2035

Does this PR introduce a user-facing change?:

NONE

Warning: The way we're injecting the address pools into the test is bad. I don't like it. However, I think at this point with GA in the next few weeks, trying to make this better would require some kind of fundamental change to the test suite which we don't have time for. If you have any great ideas for alternatives that are simple, that would be lovely. If your PR comments are going to be something like "man we really need proper templating in the test suite" please note that this will probably have to wait for later.

[k8s-ci-robot]

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This pull-request has been approved by: shaneutt

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[shaneutt]

This is now passing in Blixt, albeit I had to add several hacks to deal with the fact that our test suite is currently expecting if you do Gateway you must support HTTP (filed an issue for this in #2403). Ready for review.

[robscott]

Thanks @shaneutt!

/lgtm