Use minimum OS flags for watchOS and tvOS actions.
Use minimum OS flags for watchOS and tvOS actions.

Also:
  - Move minimum os information into AppleConfiguration
  - Update watchos and tvos minimum version defaulting behavior
    such that, if unspecified in flags, the minimum OS is equal
     to the SDK version.
  - Expose Apple Platform to apple_common in skylark

--
MOS_MIGRATED_REVID=134712763

bazelbuild/tulsi,pinterest/tulsi,pinterest/tulsi,bazelbuild/tulsi,bazelbuild/tulsi,bazelbuild/tulsi,bazelbuild/tulsi,pinterest/tulsi,pinterest/tulsi,bazelbuild/tulsi,pinterest/tulsi,pinterest/tulsi