When to use error vs exception attributes

[lmolkova]

We have error and exception namespaces that describe similar things with some caveats:

• not every error has a corresponding exception (e.g. when downstream service returns 503 and span would have error.type = "503" and no exception thrown
• not every exception is an error (see OTEP: Recording exceptions as log based events opentelemetry-specification#4333 for some examples)
• exception is a language/specific concept. E.g. where Java client library would throw, golang or rust would return error, but semantic conventions should be as language-agnostic as possible.

Combining it with evolving guidance on reporting (terminal) exception details on the spans in open-telemetry/opentelemetry-specification#4430 and #1992, we'll have an overlap between exceptions and error attributes on spans and logs.

We need to update error-recording guidance and explain when to populate error, exception or both sets of attributes.