eolian: check whether events conflict in inheritance tree (off)

eolian: check whether events conflict in inheritance tree (off)

Previously, the EOLIAN_EVENT_REDEF_WARN environment variable
enabled extra checks that would include events in checking
conflicts against methods. Since this is probably not necessary
and naming events the same as methods is perfectly fine in itself,
relax this rule and check events completely independently.

In practice, this will disallow using the same name for two
events within the same inheritance tree, which is desirable
in longer term, but cannot be enabled just yet because we have
too many of those conflicts. But it also allows the events to
be named the same as methods or parts, which is fine and was not
possible before.