S1186: also inspect empty `set` and `init` and empty local functions

[andrei-epure-sonarsource]

Rule S1186 (EmptyMethod S1186) currently looks only at method bodies, and doesn't raise when seeing empty set or init (for C# 9).

It would make sense to raise on

• empty set and init as these are actually void methods as well.
• empy local functions

Remark: add and remove for events are both void, and empty method detection can be done for those too. A dedicated issue exists: #8599