Improve the KMP SDK

[buenaflor]

Description

Meta issue for tracking the most important improvements we can do for the SDK currently

Tasks

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1. Use trimmed headers instead of cocoapods for Apple targets #74
   Platform: KMP Type: Refactoring +2
2. [Gradle Plugin] Add support for creating a dynamic library when using SPM and Cocoapods (not kotlin cocoapods) #108
   1 of 1
   Platform: KMP +1
3. [Gradle Plugin] Better support for tests not working on cocoa targets #191
   Platform: KMP +1
4. [Gradle Plugin] Enforce Cocoa SDK version #174
   Platform: KMP +1

Docs

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1. Update getting started docs to use Gradle Plugin by default, keep current version as separate page

Optional / nice-to-have / later

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1. Gradle plugin: upload proguard & dsyms directly from the gradle plugin This is blocked by the SAGP multi module rework
2. Refactor KMP plugin to work on root project level for multi module apps