Support byte arrays

[arendjr]

The OpenTelemetry log standard, which we are basing the log format in the provider protocol on, uses 16-byte arrays for the TraceId and SpanId. In order to correctly add these fields to the protocol, fp-bindgen needs to support byte arrays.

Alternatives

• Use Vec<u8> ID types - this is possible but less than ideal because we need to check that the array is the correct length
• Use String ID types - also less than ideal because we need to check the format and need to ensure that IDs are represented consistently (upper/lower case and with/without dashes)
• Support the UUID type - the TraceId and SpanId do not necessarily need to be valid UUIDs, so this is not a good solution for this use case.

cc @Zagitta @emschwartz