Remove nginx bwdserver

[pbiggar]

Part 1 of #3630

This removes nginx from the BwdServer. We needed nginx for a couple of reasons in the past that are no longer necessary or can be handled in other (better) ways:

• we needed some form of way to protect the app from expensive requests without processing them or recompiling and redeploying the whole thing. nginx gave us a quick way to update the config and restart the containers - instead we can use cloud armor, which is better at it

• we needed to support requests with missing content-lengths, as users like to make POST requests from curl sometimes and getting the right content-length is annoying. Now kestrel supports omitting the content-length header

• we needed to proxy requests to other servers for darklang.com, but now we've split the ApiServer from the BwdServer so it's not as important

• we needed to do gzip on large returned files. Admittedly nginx is better at that than kestrel but it can still be done in kestrel

• ultimately, i want to remove it as it's "yet another thing to understand" and I'd rather remove a complex step from our infra

This removes nginx from bwdserver only, including removing the deployment/k8s config files.

One major problem was that the test suite had a lot of files with the wrong content-length, which nginx papered over. So a lot of this PR is making sure the content-length is right in all the test files, and adding support to the test suite to make sure of that.

[pbiggar]

The predeployment checks CI job failed - that's fine, there's a different config and we'll just have bwdserver down for a few minutes. Since it's prerelease it doesn't matter.

[StachuDotNet]

Great!

[pbiggar]

• do shipit manual apply just before merging