possible deadlock with AWSPinpointAnalyticsClient submitEvents

[ruirodrigues-eyenov]

Describe the bug
AWSPinpointAnalyticsClient:submitEvents does a dispatch_sync(dispatch_get_main_queue(), to get [UIApplication sharedApplication] isRegisteredForRemoteNotifications] result. A dispatch_sync on main queue can lead to a deadlock when events are sent from queues besides the main queue.

To Reproduce
Send an event from a queue other than main queue and block main queue would be the easiest:

DispatchQueue.main.async {
    let waiting = DispatchSemaphore(value: 0)
    DispatchQueue.global(qos: .background).async {
        analyticsClient.record(event)
        analyticsClient.submitEvents()
        waiting.signal()
    }
    waiting.wait()
    print("event sent")
}

Which AWS service(s) are affected?
AWSPinpoint on iOS SDK

Expected behavior
Send events on a queue other than main queue without blocking.

Environment(please complete the following information):

• AWSPinpoint SDL version: 2.12.1
• Dependency Manager: Cocoapods
• Swift Version : 5.2

Device Information (please complete the following information):

• Device: iPhone, Simulator
• iOS Version: iOS 13
• Specific to simulators: no

Additional context
call stack:

* thread #1, queue = 'com.apple.main-thread', stop reason = signal SIGSTOP
....
  * AWSPinpoint`-[AWSPinpointEventRecorder submitAllEvents](self=0x000000028326b0c0, _cmd="submitAllEvents") at AWSPinpointEventRecorder.m:505:5
    AWSPinpoint`-[AWSPinpointAnalyticsClient submitEvents](self=0x00000002803f6a80, _cmd="submitEvents") at AWSPinpointAnalyticsClient.m:160:12
...

* thread #2, queue = 'livery.player.queue'
....
  * AWSPinpoint`+[AWSPinpointNotificationManager runOnMainThread:](self=AWSPinpointNotificationManager, _cmd="runOnMainThread:", codeBlock=0x000000010131b6f0) at AWSPinpointNotificationManager.m:77:9
    AWSPinpoint`+[AWSPinpointNotificationManager isNotificationEnabled](self=AWSPinpointNotificationManager, _cmd="isNotificationEnabled") at AWSPinpointNotificationManager.m:66:5
    AWSPinpoint`-[AWSPinpointEndpointProfile setEndpointOptOut:](self=0x000000028324c9c0, _cmd="setEndpointOptOut:", applicationLevelOptOut=NO) at AWSPinpointEndpointProfile.m:125:46
    AWSPinpoint`-[AWSPinpointTargetingClient currentEndpointProfile](self=0x00000002818359b0, _cmd="currentEndpointProfile") at AWSPinpointTargetingClient.m:104:5
    AWSPinpoint`-[AWSPinpointEventRecorder submitAllEvents](self=0x000000028326b0c0, _cmd="submitAllEvents") at AWSPinpointEventRecorder.m:514:28
    AWSPinpoint`-[AWSPinpointAnalyticsClient submitEvents](self=0x00000002803f6a80, _cmd="submitEvents") at AWSPinpointAnalyticsClient.m:160:12
....

[ruisebas]

This has been fixed in 2.30.2.