Improve MobileCore setApplication docs

[emdobrin]

Is there an existing issue for this?

• I have searched the existing issues

Which topic?

https://developer.adobe.com/client-sdks/home/base/mobile-core/lifecycle/#register-lifecycle-with-mobile-core-and-add-appropriate-startpause-calls

What's wrong with the content?

Missing import, or unclear examples on how the application instance can be retrieved for the usages of the MobileCore.setApplication API.

What changes do you propose?

Update all examples on setApplication(...) and indicate the application instance needs to be passed as a parameter. May include link to Android dev docs like Activity#getApplication or examples depending on the surrounding context such as
MobileCore.setApplication(this) or MobileCore.setApplication(activity.getApplication())

Anything else that can help to cover this?

No response