add wallet-swift based on uniffi-bindgen

[eugene-babichenko]

• Provide a valid Swift module
• Generate uniffi files into that Swift module
• Provide a simple script to build a framework

TBD

• Change variant names in PayloadTypeConfig - they conflict with Swift keywords
• Build this framework for multiple platforms as .xcframework. Should build for iOS and sim.
• Use the framework in Cordova plugin

[ecioppettini]

Just adding something here.

If we add the auto-generated code to source control, I think we should also add a CI job that verifies that it is up to date, since if we upgrade uniffi (to 0.17.0) for example, the generated code would have to be regenerated too, otherwise you get an error (a runtime link error, in java).

Otherwise, we could just upload the auto-generated code to the tags/releases, but keep it out of source control.