Make it possible to disable search through appsettings

[Stefan-Truelime]

Is your feature request related to a problem? Please describe.
When upgrading to to kentico 29.0.0 we encountered some issues with the azure ai search package. #11

Describe the solution you'd like
It would be nice if we can enable/disable the azure ai search in the appsettings.json like this

  "CMSAzureSearch": {
    "SearchServiceEnabled" : false //default would be true
    "SearchServiceEndPoint": "https://my-endpoint.net",
    "SearchServiceAdminApiKey": "my-admin-api-key",
    "SearchServiceQueryApiKey": "my-query-api-key"
  }

Describe alternatives you've considered
for now clearing out the SearchServiceEndPoint also 'works' i'm now able to publish pages again, but eventlog is flowing with errors

Additional context
in case for any future issue, we can just disable search and continue with our work

[liparova]

Thank you for bringing this to our attention. We'll examine it internally and keep you updated on our progress.