Swift PM fixes and Swift only

[marandaneto]

What does this PR do?

SPM isn't happy with mixed languages, so we could either split the ObjC bits (NSData) in a new package or replace it altogether, I choose the later.

Where should the reviewer start?

How should this be manually tested?

Any background context you want to provide?

What are the relevant tickets?

Screenshots or screencasts (if UI/UX change)

Questions:

• Does the docs need an update?
• Are there any security concerns?
• Do we need to update engineering / success?