Python Emitter should auto-install or detect the missing dependencies for un-branded scenario

[lirenhe]

Clear and concise description of the problem

In order to let vscode typespec extension report the missing dependencies to run codegen, C# Emitter should have the ability to detect the missing dependencies in the target machine for un-branded scenario and return the correct message.

Please check for more details: #5166

Checklist

• Follow our Code of Conduct
• Read the docs.
• Check that there isn't already an issue that request the same feature to avoid creating a duplicate.

[lirenhe]

Let's try to ensure all dependencies could be auto installed by using npm install.

[lmazuel]

@msyyc let's close this issue only when we got Pyodide version released, and we can put the Python version here as a comment.

[msyyc]

Yeah, after #5289 or #4784 merged, we could close this issue with new emitter version commented.

[msyyc]

https://www.npmjs.com/package/@typespec/http-client-python/v/0.5.0 is released.