Fix off-by-one regression in AbstractMethodMockingControl

This commit fixes the off-by-one regression accidentally introduced in
commit 55961544a722e827f2e0dfe8012d7b576d652f93.

Specifically, this fix ensures that the correct recorded call is
indexed in the 'calls' list in the implementation of
AbstractMethodMockingControl.Expectations.nextCall().

In addition, this commit improves the Javadoc for
AbstractMethodMockingControl, @MockStaticEntityMethods, and
AnnotationDrivenStaticEntityMockingControl and introduces a proper
toString() implementation for the internal Expectations.Call class in
AbstractMethodMockingControl. Furthermore, code from the obsolete
Delegate test class has been inlined in
AnnotationDrivenStaticEntityMockingControlTests.

Issue: SPR-11385, SPR-10885