IDE Channel Client: Have a generic OnMessageReceived (backport #18501)

[mergify]

GitHub Issue (If applicable): closes: #18448

PR Type

What kind of change does this PR introduce?

• Refactoring (no functional changes, no api changes)

What is the current behavior?

We have several messages and events on the IDEChannelClient.

What is the new behavior?

Now we only have one, and the messages are being handled by the EntryPoint.

PR Checklist

Please check if your PR fulfills the following requirements:

• Docs have been added/updated which fit documentation template (for bug fixes / features)
• Unit Tests and/or UI Tests for the changes have been added (for bug fixes / features) (if applicable)
• Validated PR Screenshots Compare Test Run results.
• Contains NO breaking changes
• Associated with an issue (GitHub or internal) and uses the automatic close keywords.
• Commits must be following the Conventional Commits specification.

Other information

Internal Issue (If applicable):

---

This is an automatic backport of pull request #18501 done by [Mergify](https://mergify.com).

[jeromelaban]

Backport is not needed.

[unodevops]

🤖 Your Docs stage site is ready! Visit it here: https://unodocsprstaging.z13.web.core.windows.net/pr-18534/index.html

[dr1rrb]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 2 pipeline(s).