Create CI job which aggregates and evaluates HW test results

[multiplemonomials]

The final part of the hardware testing CI system will be making two CI jobs.

Job #⁠1 will run after the hardware test jobs for an un-merged PR. It will collect all the JUnit test reports from each hardware test, parse them in to SQLite, then run the algorithm from mbed-ce/mbed-ce-test-tools#3 to determine if the tests passed. Finally, it will write status back to the pull request.

Job #⁠2 will run after a PR merges to master. It will take the SQLite database generated by on-target tests and merge it with the "old" sqlite database, such that test data for targets whose tests weren't run in this PR is copied over from the old database into the new one. Finally, it will publish the new database into some publicly accessible location such that it can be used in future runs of job #1.