Exclude overloaded from equals & hashCode in MethodOverride

Prior to this commit, the inclusion of the 'overloaded' flag in the
implementations of equals() and hashCode() in MethodOverride could lead
to adverse effects in the outcome of equals() in AbstractBeanDefinition.

For example, given two bean definitions A and B that represent the
exact same bean definition metadata for a bean that relies on method
injection, if A has been validated and B has not, then A.equals(B) will
potentially return false, which is not acceptable behavior.

This commit addresses this issue by removing the 'overloaded' flag from
the implementations of equals() and hashCode() for MethodOverride.

Issue: SPR-11420