Add public API for performance tracing

[mrtotem]

Goal

Add public API for performance tracing (aka Spans).

Testing

Unit tests and play tests were added according to the current test base.

Release Notes

WHAT: Introduces Embrace performance tracing.
WHY: Allows customers to create traces to measure the time it takes for operations in their app to complete.
WHO: Any customer who wants to be an early adopter of Performance Tracing.

[notion-workspace[bot]]

Add internal API to the Unity iOS provider regarding performance tracing

[notion-workspace[bot]]

Add internal API to the Unity Android provider regarding performance tracing

[notion-workspace[bot]]

Add public API for performance tracing - Unity