Create check runs per linter

[ericwb]

Is your feature request related to a problem? Please describe.
So today, we have a single Check run named Precaution that runs multiple linters within it.

A better model might be to utilize GitHubs support to run multiple "check runs" per app.
Each run would have it's own status and could be re-run individually in case of error. Each check run could also be customized to be appropriate for the linter in use. Additional, the runs would run in parallel.

Describe the solution you'd like
One check suite named Precaution with check runs:

• Bandit
• Gosec
• tslint

Describe alternatives you've considered
n/a

Additional context
If you look at other GitHub apps, they make use of multiple runs.

[ericwb]

This would also mean we could drop the merge_reports.js we are currently using.