Don't modify non-configuration files outside of the generation namespace

[mccoyp]

For packages that have a convenience layer, generating code from TSP shouldn't disrupt convenience-layer packaging. For example, in azure-keyvault-keys we emit code into an azure/keyvault/keys/_generated namespace -- code outside this namespace is a convenience layer.

Though emitted code is correctly put in the _generated namespace, __init__.py files outside this folder are modified to remove convenience layer exports. These files should instead be left as-is.

Tangentially related: generation produces an apiview-properties.json file at the top level of the package. The references in this file seem to be for generated code though, so we would prefer to not generate this file for a library with a convenience layer.

[msyyc]

@mccoyp I make a PR #7982 to avoid overwrite your customized init and we will try to release a new version of python emitter as soon as possible.

[msyyc]

As for apiview-properties.json, it is generated by design for flavor: azure. We will discuss about whether to add a flag for user to disable the generation. @iscai-msft for awareness.