Array Support for EAP

[Dav1dde]

We want to rollout Array support for EAP based items. This includes trace metrics, logs, spans.

This will only be supported for SpanV2 (+ OTLP) not SpanV1, for SpanV1 we keep the stringification of arrays and objects. This will allow us to stay backwards compatible, that also means only span streaming will benefit from arrays and in the future objects.

For OTLP this is a slight breaking change, as it currently does the stringification. We accept this breaking change.

For all other types (trace metrics, logs, spanv2) this is not a breaking change, since we consistently rejected arrays and objects.

This means we need to extend the EAP Attribute protocol to allow arrays.

For now we only want to support scalar arrays (no objects or other arrays nested in arrays).

We will allow arrays with mixed scalars.

Very early draft PR sketching code which needs to be changed: https://github.com/getsentry/relay/pull/5394

[linear[bot]]

RELAY-179