Feature Request: Allow sending multiple messages at once

Description

We generate workflow summaries from GHA and format each job as a Block, then post them to a notification channel for job status notifications. Recently, we encountered an issue where some workflows had more than 50 jobs. This exceeds the maximum number of blocks we can post at once. That is reasonable, and our solution is to generate multiple messages and post them in a thread. We do not always know how many messages we must submit since the summary is performed in a shared workflow. In order to do this I am left with 3 bad options:

1. Send each message as part of a matrix job; this means each message consumes a self-hosted ARC runner, which seems excessive
2. Fork the action ourselves and add support
3. Do not use the action and fall back to making API calls ourselves

It would be great if there were some way of passing in multiple messages.

What type of issue is this? (place an x in one of the [ ])

• bug
• enhancement (feature request)
• question
• documentation related
• example code related
• testing related
• discussion

Requirements (place an x in each of the [ ])

• I've read and understood the Contributing guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.
• I've searched for any related issues and avoided creating a duplicate issue.

The issue names no repository files, tests, or entry points; begin by locating the GitHub Action's message submission path and its shared-workflow inputs. Compare the current single-message behavior with the requested multiple-message and threaded-posting flow, and define completion as supporting an unknown number of messages without requiring separate matrix jobs.