[Logs] Support custom user-defined log export formats

### Problem Statement

A teams customer is looking to customize the output of exported logs from either the UI or API that result in a desired format, like this UI example, `[redacted]sentry.io/explore/logs?logsFields=timestamp&logsFields=message&logsSortBys=-timestamp`:

The following team options did not provide the log output format they needed:
* [How can I export Sentry data?](https://sentry.zendesk.com/hc/en-us/articles/27675393258779-How-can-I-export-Sentry-data)
* [Data forwarding](https://docs.sentry.io/organization/integrations/data-forwarding/)
* Export via API
* [Timeseries API endpoint](https://docs.sentry.io/api/explore/query-explore-events-in-timeseries-format/)
* [List Events API endpoint](https://sentry.io/api/0/projects/:organization_slug/:project_slug/events/)

### Solution Brainstorm

An option to both create a customizable logging format, to the extent it can mimic our UI presentation in Explore, and then select that format option if programmatically extracted via API.

### Product Area

APIs

Start by reviewing the Explore logs UI example and the documented Timeseries and List Events API endpoints, along with the existing data-export and data-forwarding options. Define how a user-created log format would be selected and represented for API extraction; done means the required custom output can be configured and retrieved programmatically.

Written by the indexing model from the issue text.