[minor] Improve SLS flow for various configurations

[rawa-resul]

Description

• Removed 13. Generate SLSCfg tasks from ibm/mas_devops/roles/sls/tasks/install/main.yml
• Set sls_action to either ["install", "uninstall"] because these are the only roles we have
• Set sls_action for the tasks/gencfg/main.yml role to either ["install", "gencfg"]
  • We want this role to run either after an install of SLS or just by itself if all we need to do is to generate the SlsCfg
• Improved ibm/mas_devops/roles/sls/tasks/gencfg/main.yml role
  • We have clear tasks for when we use it on a fresh install, existing instance or external SLS

Testing

• All of the above have been tested via the CLI