Convert Convention.methodCallParameterBuilder to a read-only public property.
Introduce ConventionRunner, a trivial wrapper around Convention.Execute, so that deprecated Convention.Execute can have a new home.
Rephrase Convention.Execute to refer to Convention properties via a variable of type Convention, which happens to equal *this*, to ease the upcoming move of Convention.Execute to a different class.
Move Convention.Execute(...) and Convention.CasesForMethod(...) out of Convention and into ConventionRunner (no substantive changes).
Move tests of ConventionRunner to their own test class (no substantive change).