Refactor File Service

The file service was initially designed with a basic workflow in mind and didn't cover all the potential use cases that would benefit from having a dedicated file interface to the provider platform. In order to expand the file service features, we propose having a design session with a better alignment with its intended use and supporting more scalable scenarios:

Here are a few suggestion:

1. decouple the getLocation from the put file operations
2. distinguish landing zone operations from file operations
3. rename API calls to be more functionally significant
4. add a put file operation so that applications can iterate or parallelize
5. support no-database implementation for providers that can retrieve meta-data from the Blob (ex, POSIX-like)
6. support POSIX interop (to be discussed)
7. add a create "container" operation to allow the following flow

• create container, returns SAS token
• iterate through a number of files, upload files (upload can be done in place);
• close container, return file list

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• File service should have functionality to access file by FileID (FileID -> SignedURL)