Add metadata when submitting tuxbuild json

[jscook2345]

Metadata to exclude:

• build_key
• build_status
• client_token
• tuxbuild_status
• status_message

Metadata to add from tuxbuild download url

• tuxmake reproducer. download or full text?

[jscook2345]

@roxell raised the following issue about the build summary when metadata is added.

The metadata in the build summary is a bit confusing because of how it is listed. It's not organized by each test case, where it does make more sense.

Incomplete example:

https://qa-reports.linaro.org/~anders.roxell/lkft-linux-next-master/build/next-20201120/?failures_only=false#!#test-results

[jscook2345]

All of this metadata can be gotten from the tuxbuild.json file. I think it can be used similar to how we add results.

[chaws]

The build metadata is a merge of all testruns' metadata: https://github.com/Linaro/squad/blob/1.30/squad/core/models.py#L411. IMHO I think it's OK to be like that so all necessary info will be the first thing to see when going to a build page.

[jscook2345]

@chaws Sounds good. We just need to make sure we extract some metadata from the tuxbuild.json file as well.