Previously, OAuth2MethodSecurityConfiguration set the
PermissionEvaluator on the expression evaluator by looking in the
context for a PermissionEvaluator bean. This is unnecessary as
GlobalMethodSecurityConfiguration already does the same thing and does
so after the post-processor in OAuth2MethodSecurityConfiguration has
run. This commit removes the redundant logic and adds tests to check
that both the PermissionEvaluator and the RoleHierarchy are set use
beans in the context.

Closes gh-7979