Allow reloading the config without a restart.

**Is your feature request related to a problem? Please describe.**

In the fluent-operator we use CRDs that generate the eventual fluentbit configuration. To make fluentbit processes restart we are building a wrapper image that adds this logic for fluentbit to restart the process.

**Describe the solution you'd like**

Would be great if fluent-bit has this logic built-in so we don't have to build this wrapper image for the operator.

- https://github.com/fluent/fluent-operator/blob/master/cmd/fluent-watcher/fluentbit/Dockerfile
- https://github.com/fluent/fluent-operator/blob/master/cmd/fluent-watcher/fluentbit/main.go

Unfortunately our team doesn't have the C skills to make that happen.

**Describe alternatives you've considered**

Continue maintaining this small wrapper and continue managing releases.

**Additional context**

We want to simplify operator releases to make it easier to keep on track with fluent-bit releases.

See here what we want to remove:

- https://github.com/fluent/fluent-operator/tree/master/cmd/fluent-watcher/fluentbit
- https://github.com/fluent/fluent-operator/blob/master/.github/workflows/build-fluentbit-image.yaml
- https://github.com/fluent/fluent-operator/blob/master/.github/workflows/bump-fluent-bit-version.yaml

So we only have to update the version for the helm chart and we don't have to release another image wrapping fluent-bit with this small go binary to reload the process on config changes.