Use ApplyObject function for creating and updating objects

This MR re-implements GitLabReconciler's createOrPatch function with ApplyObject, which imitates kubectl apply. It requires this function that is implemented in !476 (merged).

This MR also removes the unused return boolean argument of createOrPatch function.

Testing

1. Deploy the Operator with latest image of this branch:

     helm upgrade \
       --install \
       gitlab-operator deploy/chart \
       --set image.tag=581-fix-apply-config-change@sha256:7513eda8ed6740b916ee8fe951ca63997ec143a7191e41bbf45287fbc648f3db

2. Deploy a GitLab instance with:

   # example-gitlab.yaml
   apiVersion: apps.gitlab.com/v1beta1
   kind: GitLab
   metadata:
     name: example
   spec:
     chart:
       version: "6.1.0"
       values:
         global:
           hosts:
             domain: issue-581.h.k8s-ft.win
         certmanager-issuer:
           email: me@example.com
         gitlab:
           gitlab-shell:
             sshDaemon: openssh

   and then:

   kubectl apply -f example-gitlab.yaml

3. Wait until the instance id deployed.

4. Change gitlab.gitlab-shell.sshDaemon from openssh to gitlab-sshd and update the instance.

5. You should see that gitlab-shell Deployment is updated successfully with the new changes.

Closes #581 (closed)

Closes #574 (closed)

Closes #683 (closed)

Closes #697 (closed)

Closes #698 (closed)