[Unbranded Client CodeGen] We could generate client SDK without tspconfig.yaml

[lirenhe]

Clear and concise description of the problem

Please verify whether we could generate code without tspconfig.yaml and we need to support this.
The SDK generation should use the default config settings.

Verify & Fix

Beta Give feedback

1. Emitter crash if no tspconfig file Azure/autorest.python#2933
   bug +1
   
2. CSharp Emitter should work correctly with no tspconfig file Azure/autorest.csharp#5181
   v3 +1
   

   
3. Java Emitter should work correctly with no tspconfig file Azure/autorest.java#2989
   +0
4. The emitter for JS Modular should work correctly with no tspconfig file Azure/autorest.typescript#2930
   non-azure p0 +2

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