Exclusive WriteableRegistry for plugins/modules/libraries

[parasjain1]

Is your feature request related to a problem? Please describe.
In #7780 we've introduced support for opensearch modules, plugins or libraries to be able to register their own writer and reader implementations.

There's a concern with ensuring that the class identifier byte be kept unique across all such implementations.

WriteableRegistry::registerReader() will throw an exception if the ordinal byte used to register the reader already exists for some other reader in the READER_REGISTRY, but we could still register a reader using the same byte as for JodaCompatibleZonedDateTime from within a static block in Security Plugin and successfully execute the security plugin unit tests. This shall fail during runtime though.

Describe the solution you'd like

Have external modules/plugins/libraries to optionally maintain their own WriteableRegistry to avoid type ID collision when using writeGenericValue and readGenericValue. Reference to this registry can either be passed to StreamInput/StreamOutput constructors or to the writeGenericValue, readGenericValue methods. When passed, the StreamInput/StreamOutput will use this registry instead of the "core" one.

As of now BaseWriteable.WriteableRegistry is just a utility class with static maps that hold readers/writers. This will need refactoring to support creation of registry objects.

Describe alternatives you've considered
Reserving exclusive offsets or byte ranges for each plugin/module type IDs - This won't scale well as we reserve one byte for type ID with 256 possible values only. Further, it'd be counterintuitive wrt the idea of decoupling core from plugins/modules as we'd have to maintain the offset/range information for plugins within core.

relates to #7780
relates to #5910
relates to #7821

[minalsha]

@nknize @dblock any thought on this enhancement request?

[nknize]

I think we should look at converging on NamedWriteableRegistry by adding Writer support and get away from trappy read/writeGeneric.

[nknize]

@minalsha I opened a meta issue where I'll track my prerequisite changes that need to merge in order to cut over to the NamedWriteableRegistry from the current Streamables registry.