Splitting the operations in two clients and have clients in different namespace

[msyyc]

When trying Splitting the operations in two clients and have clients in different namespace, I find that current cadl-python can't handle it directly.

• client.cadl: https://github.com/Azure/autorest.python/blob/clients-in-different-namespace/packages/cadl-python/inference/client.cadl

There are two bugs in generated code:
(1) wrong import

autorest.python/packages/cadl-python/inference/generated_code/azure/openai/completion/_operations/_operations.py

Line 27 in fb02574

from .. import models as _models

When referring to models in completion/_operations.py, the relative path shall be ... instead of ..:
f89a946#diff-593f9c3ac94b68a7e8f3f0d0564b21ecaf457c6caa12a39e1ca65fac0023e974
(2) wrong config name in _vendor.py

autorest.python/packages/cadl-python/inference/generated_code/azure/openai/completion/_vendor.py

Line 11 in fb02574

from ._configuration import EmbeddingClientConfiguration

it shall be :

from ._configuration import CompletionClientConfiguration