Serialize more coders via URN + Class name

If the size of serializing Standard Coders becomes too large, an arbitrary Standard Coder can be encoded, alongside its components, via an URN and looking up the class when it is to be deserialized.

See https://github.com/tgroh/beam/commit/070854845346d8e4df824e4aa374688bd095c2c6 as an example

Imported from Jira [BEAM-1939](https://issues.apache.org/jira/browse/BEAM-1939). Original Jira may contain additional context.
Reported by: tgroh.

Start by reviewing the referenced example commit and the Apache Beam coder serialization and deserialization entry points. Define how a Standard Coder is represented by a URN plus its components, then verify that deserialization can look up the corresponding class and reconstruct the coder without excessive serialized size.

Written by the indexing model from the issue text.