[Security Solution][Detection Alerts] Create common type for dot notation fields

[dplumlee]

With the new addition of dot notation fields in the RAC initiative, we are finding a lot of bugs created by our code's assumption of nested notations for all fields. There is currently no uniform way to handle these new types and we need to create some shared method of Typing code between the front end and back end to make it easier for devs to navigate the new field names

Temporary type changes have been made in certain PRs already that will need to be converted to a more permanent solution when finished

[elasticmachine]

Pinging @elastic/security-solution (Team: SecuritySolution)

[dhurley14]

I think this might be an example of something where the type interpreted by typescript doesn't match with what is defined in the non-flattened version https://github.com/elastic/kibana/pull/123324/files#r787241301

[elasticmachine]

Pinging @elastic/security-detections-response (Team:Detections and Resp)