docs: Added documentation for monitoring all namespaces and stripping container limits

Bump to prometheus-operator 0.42.1 and update all deps

Migrate CI to github actions

Signed-off-by: Damien Grisonnet <dgrisonn@redhat.com>

tests: allow easy test paralelization

Use prometheus-operator mixin

Fixing issues with kube-rbac-proxy when importing kube-prometheus as a library

Use absolut jsonnet imports whenever possible

There are still some dependencies that we need to make work to fully
deactivate the legacyImports in the future. I'll start opening PRs
against those other repositories.

Update dependencies and most importantly Prometheus Operator to v0.42.0

Bump kube rbac proxy to v0.6.0

Signed-off-by: Damien Grisonnet <dgrisonn@redhat.com>

Signed-off-by: Damien Grisonnet <dgrisonn@redhat.com>

Bump to kubernetes 1.19.0

Argocd examples

Removed EKS patch from example

node-exporter: set maxUnavailable to 10%

This daemonset doesn't affect workload availability so allow its rollout to
be parallelized.

Support utf8 in external file alertmanager config

This could have been achieved either by switching to stringData, or doing
`std.base64(std.encodeUTF8($._config.alertmanager.config))` as per
google/jsonnet#575

I went with the former, because it's:
1. Easier to read existing config
2. Consistent with the way jsonnet object-based config is written just above

Grammatical correction in README