native_json codec is not serializing/deserializing EventMetadata.

[neuronull]

Discovered while adding to the Vector protobuf definition for the native codec, as part of #18405.

Doing so necessitated regenerating the fixture files used in the native codec unit tests.
This led to a test failure in current_native_decoding_matches , which compares the Event that is created by deserializng a json fixture file with a proto fixture file, that should have been encoded with the same Event when the files were generated.

The offending bits are that the EventMetadata.value is not being handled by the native_json codec, but it is being handled by the native (protobuf) codec. This boils down to the fact that the EventMetadata is being skipped by the serde deserialize/serialize for the Event structs. This could largely be due to the fact that not skipping that field means that the EventMetadata must satisfy the trait requirements of configurable_component.

There are basically three problems here:

1. the native_json codec it seems should be handling the value field of EventMetadata.
2. the unit test current_native_decoding_matches fails on master due to 1
3. methodology we are using to perform the unit tests around the native codecs, is clearly currently prone to errors, as it involves applying a patch file, which inherently gets out of date over time and if we don't regenerate the data files often enough, we can get into a situation such as this, where we've had multiple releases containing this inconsistency.

[dsmith3197]

This would be fixed by #18779