Update/revisit codecov integration/config

[blueyed]

In/for #8 apparently a yaml for the organization was created: https://codecov.io/account/gh/jazzband/yaml

I think we should use the new integration via https://github.com/apps/codecov/installations/new/permissions?target_id=15129049 instead, and remove the project config, as it seems to affect all projects, and overrides the default config.

But it might also make sense to set a default config here, given that most projects do not like codecov comments for example.

The following might be good, but includes comments:

coverage:
  status:
    project: yes
    patch: yes
    changes: yes

comment:
  layout: "header, diff, flags"
  behavior: default
  require_changes: no

Ref: https://docs.codecov.io/docs/codecov-yaml
Ref: https://docs.codecov.io/docs/pull-request-comments

[blueyed]

Codecov is posting comments for PRs with jazzband/pip-tools however, which does not have a custom config (file or via the UI): jazzband/pip-tools#754 (comment)

Therefore it seems to use default settings for this there.

[jezdez]

Yeah, I think since I've enabled the GitHub app for Codecov the old org wide settings simply don't make any sense anymore and the bot setting may even be ignored. Removing the org wide setting..

[jezdez]

I'm not sure about the rest of the config above, would you mind commenting the code sample with what each does?