Startup of platform manager and system layer has some issues around the wake event (WakeEvent) on Darwin

[bzbarsky-apple]

Problem

Run chip-tool. One of the first log lines is:

[1660308661009] [56112:126013718] CHIP: [DL] RequestCallbackOnPendingRead with no dispatch queue: callback may not work (might be ok in tests)

What's happening here is that the Darwin PlatformManagerImpl::_InitChipStack does these, in order:

1. Create work queue.
2. Call GenericPlatformManagerImpl::_InitChipStack
3. Call DeviceLayer::SystemLayer().SetDispatchQueue()

During the execution of GenericPlatformManagerImpl::_InitChipStack,SystemLayer().Init() is called, which lands in LayerImplSelect::Init, which tries to set up the WakeEvent bits, which lands in LayerImplSelect::RequestCallbackOnPendingRead, and we log the above because we have no dispatch queue at this point: step 3 above has not happened yet.

The practical effect is that I expect when dispatch queues are being used WakeEvent does not work on Darwin, but I assume that it's also not used on Darwin in that case; instead dispatch to queues is used.

Proposed Solution

A few options:

1. We could move SetDispatchQueue to before the GenericPlatformManagerImpl::_InitChipStack call. I think that should be safe, but @vivien-apple and @kpschoedel should check.
2. We could make the log there be a progress log, not an error log.
3. We could suppress the log during init.
4. We could do nothing....