[CBBS] Prefix common constants

What's the issue?
The way we name constants in cbbs isn't as clear as they could be, for example.

const (

	EnvironmentKMSAuthType KMSAuthType = iota

	FileKMSAuthType 

	IDAndKeyKMSAuthType

)

const (

        KMSAuthTypeEnvironment KMSAuthType = iota

        KMSAuthTypeFile

        KMSAuthTypeIDAndKey

)

This naming method means:

1. We prefix the constant with the type (rather than postfix/omission)
2. Text editor suggestions should be saner
3. It's clear which constants are related/grouped at a glance