Span Data Export via API

### Problem Statement

Following the pattern set by https://docs.sentry.io/api/events/ - it would be very helpful to do the same using the Spans dataset. At minimum, to be able to export Spans we log in Sentry on a regular basis to do our own data analysis.

### Solution Brainstorm

_No response_

### Product Area

Unknown

Start by reviewing the linked Sentry Events API documentation and how the Spans dataset is exposed. Define the required span export behavior and confirm that regular span data analysis can be performed through the API.

Written by the indexing model from the issue text.