Migrate Storage File to TypeSpec

Update the Storage File package to use TypeSpec instead of autorest

This is primarily an exercise to migrate the tool chain. This is NOT an exercise to
- Improve the convenience layer to latest guidelines
- Ask for new complex features in TypeSpec in order to remove already written manual convenience layer. For instance, paging in Storage couldn't be generated with autorest and was manually written. We don't plan to make TypeSpec support Storage paging out of the box, we'll just keep for now the convenience layer that exists. Easy TypeSpec update can be considered, as long as this doesn't impact the timeline in an unhealthy way.
As this is an internal toolchain update, there should be no reason to update tests or re-record tests. It's actually a great regression testing to confirm that we're able to change the internal layers of Storage, without having to touch the test folder at all
No breaking changes are allowed (APIView shouldn't even realize there was a change)

We owned this branch, and should push all tspconfig and client.tsp updates directly there (no review needed yet):
https://github.com/Azure/azure-rest-api-specs/tree/feature/file-tsp/specification/storage/data-plane/FileStorage

tsplocation should target this branch for now

More details and update on the loop paage

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