Add more granular upload-to-blob functions, refactor u2b code

[ewertons]

Checklist

• I have read the [contribution guidelines] (https://github.com/Azure/azure-iot-sdk-c/blob/main/.github/CONTRIBUTING.md).
• I added or modified the existing tests to cover the change (we do not allow our test coverage to go down).
• If this is a modification that impacts the behavior of a public API
  • I edited the corresponding document in the devdoc folder and added or modified requirements.
• I submitted this PR against the correct branch:
  • This pull-request is submitted against the main branch.
  • I have merged the latest main branch prior to submission and re-merged as needed after I took any feedback.
  • I have squashed my changes into one with a clear description of the change.

Reference/Link to the issue solved with this PR (if any)

Description of the problem

Customers cannot retry notifying Azure IoT Hub of upload completion if any failure on that step occurs.
Also adding a retry mechanism hidden in our code would not allow customers to tailor the retry to their specific needs.

Description of the solution

Expose functions in Azure IoT C SDK for customers directly create, upload and notify completion as they need.

[CIPop]

I've left a few comments.

One interesting architectural change would be to add a way to extract the URI/SAS token (constructed now internally) that could be then passed to an external Azure Blob SDK (C++ or other tool such as the high-perf az_copy CLI tool).

[CIPop]

I would rather move the list of how-to things either in the DevDoc or in a header (a single block, instead of copy/pasting everything) then referencing that doxygen block.

[CIPop]

Left a few observations about enhancing documentation.

The E2E code has some odd for loop that runs once: I assume that needs to be removed although the comment states otherwise.

[CIPop]

❤️