Replace GitLab Shell generator functions with Helm template

This MR replaces generator functions for GitLab Shell resources with objects that are created using Helm template.

The following generator functions must be replaced:

• ShellConfigMap
• ShellDeployment
• ShellSSHKeysSecret
• ShellSecret
• ShellService

Notes:

1. The required query functions are separated in !73 (merged).
2. The replacement must be validated with the custom matcher in !67 (merged).

Closes #34 (closed)