LUA filter inline code support

[chrono2002]

Adds support for "code:" inline block in LUA namespace-wide filter.
See: https://docs.fluentbit.io/manual/pipeline/filters/lua
"code | Inline LUA code instead of loading from a path via script."

None

Usage:

apiVersion: fluentbit.fluent.io/v1alpha2
kind: Filter
metadata:
  labels:
    fluentbit.fluent.io/enabled: "true"
  name: test
spec:
  match: "*"
  filters:
  - lua:
      call: converter
      protectedMode: true 
      code: |
        function converter(tag, timestamp, record)
            return 0, 0, 0
        end

[benjaminhuo]

Thanks for the PR @chrono2002 , looks like there're indent issues here.
You may need to run :

make generate
make manifests
make fmt
make vet
make docs-update

[benjaminhuo]