This adds a StringInquirer subclass EnvironmentInquirer that
predefines the three default environments as query methods, in
order to avoid dispatching through `method_missing` for every call
to those methods. The original StringInquirer was not modified due
to the side effects of having new env-related methods on it. This
new class was not implemented using lazy method definition to
avoid the open-ended possibility of defining a new method for all
query calls. The three default environments should cover a high
percentage of real-world uses, and users with custom environments
could add their own to this class.

Fixes #37803.