feat(otlp): infer span category from attributes

[mjq]

Relay assigns a category to incoming spans based on their op (see our docs for possible category values).

Unlike Sentry's op field, OTel span names aren't structured and therefore can't be used to determine the span category.

In order to support categorizing incoming OTel spans, update the span categorization algorithm to:

1. Use the incoming sentry.category attribute directly if given. This allows our SDKs to be explicit about the intended category and also lets users explicitly perform categorization in case our automatic categorization is ever incorrect.
2. Extract the category from op. This is what we do today, and will keep categorization consistent for Sentry SDK clients sending spans via transaction events now and in the future.
3. When op is missing (e.g. an OTLP span), infer the category based on the span's attributes. This will categorize incoming OTel spans based on semantic conventions.

Currently the inference only supports the five categories we use in the transaction summary page's operation filter, which is the page the Performance team is currently migrating to EAP. We'll expand it in the future as we move more of the product surface area over to support EAP/span-first/OTLP.

[mjq]

Based on our docs on categories this update seems correct (in other words, it was incorrect that this was previously missing).

[Dav1dde]

Maybe you can also find an existing integration test, which we can extend for this.