Fix Logstash keystore performance

[kaisecheng]

Fixes: #7027

Logstash has performance issue when init container creates keystore with a couple of keys.
Since Logstash 8.12.0, logstash-keystore command supports adding multiple keys in one operation.
This PR uses the command to add keys in a batch. The minimum version of Logstash currently running in ECK is 8.12.0

The steps to create keystore in Logstash

# create keystore without password
echo 'y' | bin/logstash-keystore create 
# add keys one and two
bin/logstash-keystore add one two
Enter value for one: # input ASCII and non-empty string, and then press <enter>
Added 'one' to the Logstash keystore.
Enter value for two:
Added 'two' to the Logstash keystore.

The following resources should start approximately in a minute

apiVersion: v1
kind: Secret
metadata:
  name: logstash-secure-settings
stringData:
  HELLO: HALLO
  A: "1"
  B: "2"
  C: "3"
  D: "4"
  E: "5"
  F: "6"
  G: "7"
  H: "8"
  I: "9"
  J: "10"
---
apiVersion: logstash.k8s.elastic.co/v1alpha1
kind: Logstash
metadata:
  name: logstash-sample
spec:
  version: 8.12.0
  count: 1
  pipelines:
    - pipeline.id: main
      config.string: |-
        input { exec { command => 'uptime' interval => 10 } }
        filter {
          if ("${HELLO:}" != "") {
            mutate { add_tag => ["${A}", "${B}", "${C}", "${D}", "${E}", "${F}", "${G}", "${H}", "${I}", "${J}"] }
          }
        }
  secureSettings:
    - secretName: logstash-secure-settings

[robbavey]

Works as advertised, just a couple of naming nits

[robbavey]

Suggested change

	ContainerCommand string
	CustomScript string

This may be easier to follow, if we call this CustomScript, and comment to state that this is a script to run that overrides the default Keystore script?

[robbavey]

For consistency, we might want to think about using both KeystoreCreateCommand and KeystoreAddCommand here, and in the script, or just calling out to logstash-keystore directly in the script.

[kaisecheng]

added the command for consistency

[robbavey]

LGTM other than small nit about using the same executable path consistently

[kaisecheng]

@pebrc @barkbay this is ready for ECK team to review

[pebrc]

LGTM

[kaisecheng]

@pebrc thanks for the review. This PR is ready to merge

[pebrc]

@robbavey can you approve to override your previous "change requested"?

[robbavey]

LGTM

[robbavey]

Approved