Native: Add docs for Consent feature

[kahest]

Core or SDK?

Platform/SDK

Which part? Which one?

Native

Description

The Consent feature is currently not documented for Native.

Suggested Solution

• add new page under Usage
• describe how to use the feature (set required/not required, give/revoke consent)
• describe functionality (include scenarios such as: SDK caches events before consent decision is known, and will apply the consent decision on the cached events as soon as consent is given or revoked)
• describe limitations (e.g. external crashpad handler)