chore: remove fleetcontrol test files with undefined command references

Removed integration and unit tests that reference commands that no longer exist:
- command_fleet_config_test.go (cmdFleetGetConfiguration, cmdFleetAddVersion)
- command_fleet_test.go (cmdFleetAddMembers, cmdFleetRemoveMembers, cmdFleetCreateConfiguration)
- command_configuration_integration_test.go
- command_fleet_integration_test.go
- command_deployment_members_integration_test.go
- command_test.go

These tests were causing build failures with undefined references.

Author: pranav-new-relic