[JENKINS-71956] Switching YAML serializer to Jackson to support Octal values

[Dohbedoh]

Amends #1342 and #1503.

Address the octal / decimal (de)serialization inconsistencies by using Jackson. Just proposing a minimalist Serialization utility here to handle the Serialization / Deserialization of a single resource. As anyway we are only managing YAML with single Pod resource here.

Testing done

Tested a pipeline with octal notation:

pipeline {
    agent {
        kubernetes {
            yaml '''
apiVersion: v1
kind: Pod
metadata:
  name: test
  annotations:
    com.cloudbees.sidecar-injector/inject: no
spec:
  containers:
  - name: jnlp
    volumeMounts:
      - name: ca-bundles
        mountPath: /etc/pki/ca-trust/extracted/pem/tls-ca-bundle.pem
        subPath: ca-certificates.crt
        subPath: cacerts
  volumes:
    - name: ca-bundles
      configMap:
        defaultMode: 0644
        name: ca-bundles
'''
        }
    }
    stages {
        stage('Main') {
            steps {
                sleep 600
            }
        }
    }
}

And a pipeline with decimal notation:

pipeline {
    agent {
        kubernetes {
            yaml '''
apiVersion: v1
kind: Pod
metadata:
  name: test
  annotations:
    com.cloudbees.sidecar-injector/inject: no
spec:
  containers:
  - name: jnlp
    volumeMounts:
      - name: ca-bundles
        mountPath: /etc/pki/ca-trust/extracted/pem/tls-ca-bundle.pem
        subPath: ca-certificates.crt
        subPath: cacerts
  volumes:
    - name: ca-bundles
      configMap:
        defaultMode: 420
        name: ca-bundles
'''
        }
    }
    stages {
        stage('Main') {
            steps {
                sleep 600
            }
        }
    }
}

And validate that in both cases the right permission are applied to the volume.

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