JSON format in alert body is unintentionally escaped and broken when using alert template macro

[takanau]

Issue Summary

When using alert template macro (ex: {{QUERY_RESULT_ROWS}}, cf) in alert body, the result is HTML escaped and its JSON format is broken like this:

[{'column': 1}]

Steps to Reproduce

• https://github.com/getredash/redash/blob/master/redash/models/__init__.py#L1039
• https://github.com/getredash/redash/blob/master/redash/utils/__init__.py#L139-L141

When rendering alert template, mustache_render should be used, not mustache_render_escape.

Technical details:

• Redash Version: 24.12.0-dev

I guess this problem caused by #5996 (Version: 23.09.0)

[perceptron01]

I'm also encountering this issue when trying to send alert messages to Slack.
This appears to be related to the issue reported in #7362