Trace exception recording was never stabilized

[jsuereth]

Tracing specification used to rely on semantic conventions to define how to record an exception as a Span Event. With #3489 this normative language moves back into the tracing specification. We will need to:

• Verify that the current language is enforced across SDKs
• Mark this part of the specification as stable

There were some unresolved "post-GA" issues that may need to be tackled for this:

• Exception semantic conventions and Go error return values #764
• RecordException and Span.Status #1008

Additionally related, #3198

[austinlparker]

Is this still germane @jsuereth ?

[svrnm]

@jsuereth please take a look

[trask]

resolved by #3769, @jsuereth please reopen if I missed something, thanks