Specify default provider-ci config in code

[blampe]

We currently specify config defaults here

ci-mgmt/provider-ci/internal/pkg/templates/defaults.config.yaml

Line 4 in 6de05d1

We can instead specify them in code here:

https://github.com/pulumi/ci-mgmt/blob/6de05d16ad63eeffbd88aeb476030381ffdb13b6/provider-ci/internal/pkg/config.go

[iwahbe]

I think that specifying them in the defaults file is a bit clearer. If there was a way in Go to specify a config format that was self-documenting and could generate a default file, then I'd go with that.