[Bug]: events::wait_for_event needs to be updated to match EDK2 semantics.

[joschock]

Is there an existing issue for this?

• I have searched existing issues

Current Behavior

1. wait_for_event does not signal the idle loop event (https://github.com/tianocore/edk2/blob/38370cf4924205df97b8bcaf0f184983a4b34f66/MdeModulePkg/Core/Dxe/Event/Event.c#L697)
2. wait_for_event returns an error if out_index is null, but it is an optional input and should simply be ignored if null.

Expected Behavior

function should align with edk2 semantics.

Steps To Reproduce

By inspection.

Build Environment

N/A

Version Information

Tag: patina-v8.3.0

Urgency

Low

Are you going to fix this?

I will fix it

Do you need maintainer feedback?

No maintainer feedback needed

Anything else?

No response