Add support for Kotlin's Result

[tomridder]

add the ResultCallAdapter to return Result to wrap the outcome (success/failure) of a retrofit call, instead of returning a value or throwing an exception. #3558

like

@GET("me") suspend fun getUser(): Result<User>

all the testcase in Kotlin-test package and retrofit-adapter moudle's test case has been passed

[tomridder]

@JakeWharton @codebutler hello ?anyone there