When running in --closed-world, compute effects for indirect calls by
unioning the effects of all potential functions of that type. In
--closed-world, we assume that all references originate in our module,
so the only possible functions that we don't know about are imports.
Previously [we gave up on effects
analysis](https://github.com/WebAssembly/binaryen/blob/29b2d42e8a748fbe1095696d58a52b7bf83e2253/src/passes/GlobalEffects.cpp#L83-L87)
for indirect calls.

Yields a very small byte count reduction in calcworker (3799354 -
3799297 = 57 bytes). Also shows no significant difference in Binaryen
runtime: (0.1346069 -> 0.13375045 = <1% improvement, probably within
noise). We expect more benefits after we're able to share indirect call
effects with other passes, since currently they're only seen one layer
up for callers of functions that indirectly call functions (see the
newly-added tests for examples).

Followups:
* Share effect information per type with other passes besides just via
Function::effects (#8625)
* Exclude functions that don't have an address (i.e. functions that
aren't the target of ref.func) from effect analysis ()
* Compute effects more precisely for exact + nullable/non-nullable
references

Part of #8615.