Request: Send stats as text instead of images to Slack

I think it would be nice / better if metabase would send text to Slack instead of images.

Formatting can be tough but right now the rows are even capped, rendering the entire feature less useful. Also Easy copy paste is not possible that way.

:arrow_down: Please click the :+1: reaction instead of leaving a `+1` or `update?` comment

The issue does not name a file, entry point, or test. Start by locating the Slack delivery and image-rendering paths, then determine how stats are formatted and capped; done means Slack receives copyable text containing the full result with suitable formatting.

Written by the indexing model from the issue text.