[SERV-1209] Add EOLCheck and refactor project structure

[ksclarke]

• Add a bounds checking method and test to csv_location.go (now location.go) file for reuse in all implementations of Validator
• Create more directory structure for the project since it's getting larger (incorporated Angela's checks dir but put it in a validation dir).
• Removed the .git from the module name (which is common practice, apparently)
• Updated serviceName flag in TestContainers test (it wasn't being recognized anymore)
• Added a validation check so I'd have something to test for my next ticket (and as a very simple example); it doesn't strictly require a profile but I added a NewEOLCheck method to illustrate what the idea was in terms of giving that information to the implementations.
• Renamed some types now that their packages have changed (e.g. CsvLocation -> csv.Location)