Added Metal delegate and Core as subspecs of the source pod.
* Removed manually written module map. The module map and umbrella header `TFLTensorFlowLite-umbrella.h` will be automatically generated with all the delegate headers. `TFLTensorFlowLite.h` is left for legacy purpose.
* Modified macro to make tests work with bazel and Cocoapods.
Changed some umbrella header imports to module import,
`@import TFLTensorFlowLite`.
PiperOrigin-RevId: 333012903
Change-Id: Ib743d7a3250b884fc406505f457ed55cea1ad20d
86726adc39