chore: Revert custom handling for multiple Unstructured base urls

[awalker4]

The Issue

We discovered a behavior change in the Python SDK after we merged the platform/serverless api specs. All of a sudden, the SDK level server_url param silently stopped working, and we were forced to set custom urls per function.

# The passed url is ignored and we go to our default Serverless URL. 
# You suddenly get an invalid api key error if you expected to talk to, e.g, freemium
s = UnstructuredClient(server_url="my_own_url")
s.general.partition()

#  This does the right thing
s = UnstructuredClient()
s.general.partition(server_url="my_own_url")

We had to patch some generated code in order to keep backwards compatibility, and set the SDK level server_url the way we used to. This works! However, any file in .genignore will not get updated and eventually the SDK fails to generate because of drift. The better solution is to figure out why the generated code changed on us, and fix it "upstream".

The Fix

Our SDK points to two services - the workflow API at platform.unstructuredapp.io and the older partition endpoint at api.unstructuredapp.io. We merged these two openapi specs in order to generate a combined SDK, but this meant that urls could only be resolved per operation. There is no longer a global default, so a statement like UnstructuredClient(server_url="my_own_url") is ambiguous.

The solution to all this is to go back to one default server - the platform url. The partition url is just one endpoint so it's much easier to handle as a one off. This restores the server_url behavior we had, without us having to fight with the autogenerated code.

The Diff

This pr is huge because I regenerated the relevant files. There are only a few changes that drive all of it:

overlay_client.yaml

After merging the two openapi.yaml specs, remove all child servers blocks and just keep one global config. Now every endpoint is a part of platform.unstructuredapp.io

general.py

This is now the only custom patch. In the partition (and partition_async) call, we need to swap to the right url. We do this only if the user has not already changed the default.

destinations.py, jobs.py, etc

These are the other endpoint files that are no longer patched. After regenerating, you can see the base_url logic cleans itself up. Either the user passed a server_url in the call, or we fetch the globally configured url.

test_server_urls.py

Made some tweaks to these test cases. This locks in our compatibility and asserts that we always use the right url. Users can set a custom url at the SDK init, or at the operation. We need to cover this behavior within general.partition since this has the special logic. Otherwise, make sure both url approaches work for any of the other platform operations.