According to server_parameters.md document, parameters which are declared `runtime` should have a thread-safe cpp_vartype. However this is not enforced in the validation of the *.idl files.

These can lead to some parameters not having the proper types, for example:

• https://jira.mongodb.org/browse/SERVER-119575: gTrafficRecordingDirectory
• https://jira.mongodb.org/browse/SERVER-119574: gReshardingCollectionClonerWriteThreadCount

There are other examples which can be found in the code. Can you:

• introduce some form of validation so that we prevent these errors
• drive the clean-up effort on the parameters which have the wrong type