feat: add ability to customize metrics port

[dh185221]

What this PR does / why we need it:

This change allows a user to specify a metrics port as part of their FluentBit custom resource. This is useful for those who need to use a port other than 2020.

Which issue(s) this PR fixes:

Fixes #

Does this PR introduced a user-facing change?

Added the optional `metricsPort` property in the `FluentBit` custom resource allowing users to specify a port.  Port 2020 will be used by default if this property is not set.

Additional documentation, usage docs, etc.:

An example of a partial FluentBit resource with this new property might look like this:

apiVersion: fluentbit.fluent.io/v1alpha2
kind: FluentBit
metadata:
  name: fluent-bit
  namespace: fluent
  labels:
    app.kubernetes.io/name: fluent-bit
spec:
  image: kubesphere/fluent-bit:v2.0.9
  metricsPort: 32020

[wanjunlei]

By default, fluent-bit will not start the metrics server, so does it need to change the HttpServer to true and set the HttpPort when the MetricsPort is set? Or do these need to be manually set by the user?

[dh185221]

By default, fluent-bit will not start the metrics server, so does it need to change the HttpServer to true and set the HttpPort when the MetricsPort is set? Or do these need to be manually set by the user?

I think in this case if the user specifies metricsPort inside their FluentBit resource then they would need to match that up with the port in their ClusterFluentBitConfig definition.

apiVersion: fluentbit.fluent.io/v1alpha2
kind: FluentBit
metadata:
  name: fluent-bit
  namespace: fluent
  labels:
    app.kubernetes.io/name: fluent-bit
spec:
  image: kubesphere/fluent-bit:v2.0.9
  metricsPort: 32020
  .
  .

apiVersion: fluentbit.fluent.io/v1alpha2
kind: ClusterFluentBitConfig
metadata:
  name: fluent-bit-config
  labels:
    app.kubernetes.io/name: fluent-bit
  namespace: fluent-operator
spec:
  service:
    daemon: false
    flushSeconds: 5
    httpListen: 0.0.0.0
    httpPort: 32020
    httpServer: true
    logLevel: info
    parsersFile: parsers.conf
  filterSelector:
    matchLabels:
      fluentbit.fluent.io/enabled: "true"
  inputSelector:
    matchLabels:
      fluentbit.fluent.io/enabled: "true"
  outputSelector:
    matchLabels:
      fluentbit.fluent.io/enabled: "true"

[benjaminhuo]

I think in this case if the user specifies metricsPort inside their FluentBit resource then they would need to match that up with the port in their ClusterFluentBitConfig definition.

Agree, @dh185221 can we add this to the metricsPort comments? https://github.com/fluent/fluent-operator/pull/587/files#diff-5c477d8ee7708b4cadb8cc2e2435185df0d8a187b6dc26e351b75a3d0547c422R91