@DefaultCoder annotation should work with Create

From user@beam.apache.org:

"My class is declared as follows:

@DefaultCoder(SerializableCoder.class) public class Data implements Serializable {

and it fails like this:

Caused by: org.apache.beam.sdk.coders.CannotProvideCoderException: Cannot provide coder based on value with class my.project.Data: No CoderFactory has been registered for the class."

It seems like this should work, though Create's value-based coder inference has more limitations and safety issues than usual coder inference. To investigate.

Imported from Jira [BEAM-1736](https://issues.apache.org/jira/browse/BEAM-1736). Original Jira may contain additional context.
Reported by: kenn.

The issue names Apache Beam's Create transform, value-based coder inference, and the @DefaultCoder annotation, but no files or tests. Start by tracing Create's coder inference and compare it with the reported Data example; done means determining whether the annotation should be honored without CannotProvideCoderException and documenting or covering the resulting behavior.

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