Create Issues from OpenTelemetry exceptions (OTLP exception log records and span events) #127561

Problem Statement

Applications instrumented only with OpenTelemetry can send traces and logs to Sentry's OTLP endpoints, but their exceptions never become Issues:

• Exception span events (the current default way OTel SDKs record exceptions, via span.recordException) are dropped on OTLP ingest. Sentry's docs say "All span events are dropped during ingestion".
• Exception log records (where OTel is moving exceptions: OTEP 4430, OTEL_SEMCONV_EXCEPTION_SIGNAL_OPT_IN=logs) are stored as logs only.

So OTel-only services get no Issues, alerts, grouping, suspect commits or Seer for their errors, even though the data contains everything an error event needs: exception.type, exception.message, exception.stacktrace (semconv), plus trace and span ids.

Solution Brainstorm

Build on the generic log → Issue capability in #113802, with an exception-aware path for OTel:

1. Exception log records → error Issues. Records with event_name exception / *.exception, or with exception.type / exception.message attributes, become error events. Severity sets level and handled state (FATAL/ERROR → Issue, WARN optional). The stack trace is parsed from exception.stacktrace (its format depends on the runtime), with cause chains as linked errors and the trace context kept.
2. Span events → the same path. Instead of dropping exception span events, convert them into exception log records (same attributes, plus the span's trace/span ids) so they go through step 1. Until OTel SDKs default to log-based exceptions, this covers most OTel exceptions in the wild.
3. De-duplication. In logs/dup mode, SDKs emit both a span event and a log record for the same exception. These should become one Issue (e.g. keyed on span id + message).

Additional Context

• Related: Allow creating issues from structured logs (especially error-level logs from log drains) #113802 (Issues from structured logs, generic)
• OTel: deprecating span events (OTEP 4430) · events semantic conventions
• Relay currently drops span events when converting OTLP spans (relay-spans/src/otel_to_sentry_v2.rs)