Rename `exception.*` to `error.*` (aligning with ECS)

[trask]

What are you trying to achieve?

Rename exception.* attributes to the corresponding ECS names under error.* (see open-telemetry/oteps#222 for motivation).

Rename:

• exception.type -> error.type
• exception.message -> error.message
• exception.stacktrace -> error.stack_trace
• exception.escaped -> (nothing corresponding)

[trask]

@AlexanderWert it's not clear to us the best mapping from OTel's all-in-one-string (unstructured) exception.stacktrace to ECS's multi-field/wildcard error.stack_trace.

Is error.stack_trace.text the convention for capturing an all-in-one-string (unstructured) stack trace?

[AlexanderWert]

@trask In ECS (and Elasticsearch) there are different types of strings: keyword (indexed as is for direct access) and text (optimized for search in text). A field can have both characteristics, in that case fieldname is the keyword and fieldname.text is the text type field.

error.stack_trace is such a wildcard type which is a special case of keyword type. And it also searchable, so it has in addition the error.stack_trace.text field.

For OTel semconv the keyword / wildcard typed field is relevant and we can ignore the text field.

[mwear]

I don't have strong feelings on this either way, but wanted to link two previous issues where this was discussed. #427 and its successor #697. The original proposal named the conventions error.*. It was changed due to the discussions on those PRs.