Push build/test statistics to elastic

[msimberg]

#891 pushes performance data to elastic. We should expand this to push general metrics about the builds:

• test pass/fail (Report test statistics to elastic #907)
• test time (this gets us header build times as well, Report test statistics to elastic #907 and Submit CTest results for compile-only tests to elastic #952)
• build times
• file sizes (Report library and executable file sizes to elastic from CI #958)

I think most of this would be possible to add by sending the CTest/CMake XML output, transformed to json (using https://github.com/kislyuk/yq#xml-support?), to elastic.