Fields with certain object poison Ingest Common SetProcessor's `copyFrom`

[yaauie]

The IngestCommon SetProcessor's copyFrom implementation will attempt to perform a deep copy of the value, supporting ONLY following object types:

• java.util.Map<?, ?> (recursively copies values; leaves keys unmodified)
• java.util.List<?> (recursively copies values)
• java.util.Set<?> (recursively copies values)
• byte[]
• double[][]
• double[]
• null
• java.lang.String
• java.lang.Integer
• java.lang.Long
• java.lang.Float
• java.lang.Double
• java.lang.Boolean
• java.time.ZonedDateTime
• java.util.Date

When encountering a value that is not on that list, the pipeline fails with unexpected value type [org.logstash.Timestamp] or similar.

Looking at our own Javafier implementation, the following can escape Javafier#deep and trigger the issue:

• org.logstash.Timestamp
• java.math.BigInteger
• java.math.BigDecimal

Of these, org.logstash.Timestamp can be easily represented by java.time.ZonedDateTime, and can be converted back losslessly when reconstituting the Event.

I believe the others can be solved on the Elasticsearch side.