Fix packaging of tests and resources

[theacodes]

• Don't include tests in the binary (wheel) distribution.
• Include tests in the source distribution.
• Include only .json and .proto package resources.
• Include a LICENSE with every package (extremely important for downstream packagers).
  (From Fix packaging of resources and tests #3182)

[googlebot]

So there's good news and bad news.

👍 The good news is that everyone that needs to sign a CLA (the pull request submitter and all commit authors) have done so. Everything is all good there.

😕 The bad news is that it appears that one or more commits were authored by someone other than the pull request submitter. We need to confirm that they're okay with their commits being contributed to this project. Please have them confirm that here in the pull request.

Note to project maintainer: This is a terminal state, meaning the cla/google commit status will not change from this state. It's up to you to confirm consent of the commit author(s) and merge this pull request when appropriate.

[theacodes]

I need to rebase on top of ci, will do shortly.

[googlebot]

CLAs look good, thanks!

[theacodes]

@lukesneeringer @dhermes rebased, should be good to review now.

[lukesneeringer]

LGTM once I get ci in.

[theacodes]

Since ci is already in review and this won't pass while targeting that branch, do we want to go ahead and merge this into ci?

[dhermes]

👍 to what @jonparrott said

[lukesneeringer]

Yep, doing it.