Update azure blob SDK version

[mdrichardson]

Partial fix for #1343

Please Read

#1343 is for porting over Azure Blobs and Queues from .NET and JS. In those SDK, Azure Blobs was plural-ified from Bot.Builder.Azure.BlobStorage to ...Blob*s*Storage, adding a new Blob Storage library. This was done because of a dependency namespace conflict that would break binary compatibility.

As far as I can tell, we can't do this in the Python SDK because that would require the SDK to depend on two different versions of azure.storage.blob. The current version in our SDK is 2.1, but the most recent version is 12.7.1. This PR updates to 12.7.0 because there's an msrest dependency conflict at 122.7.1.

So, this PR updates our current blob_storage to just use the new SDK. If approved, I'll then add an additional queue_storage.

There's some pretty big changes in the the internal code for this PR due to:

1. Forced changes when upgrading azure.storage.blob 10 major versions, and
2. Trying to make the code more or less match .NET's BlobsStorage and Node's BlobsStorage

Testing

All tests pass when running Storage Emulator and setting this to True so the tests run.

The warning are all of this nature:

...but per @axelsrz, that's expected for our SDK and Python 3.8.

Backwards Compatibility Testing

I also tested by:

1. Downloading State Management sample and converting to use original blob_storage
2. Conversed with bot
3. Removed botbuilder.azure from sample, then added new blob_storage.py and ensured it used that
4. Started a conversation with the bot as the same user
5. Bot was able to retrieve previous conversation data from older blob_storage

Conversation and UserState data still look the same:

I'm not sure why e_tag gets quotes placed around it. I don't do any encoding, so I think it's something done by azure.storage.blob. I sort of mitigate it here

Note

This library will eventually benefit from investigating some of the Blob Storage options, but I won't have the bandwidth to land this in R12.

[mdrichardson]

I didn't see anything regarding public access referenced in .NET or JS and tests all passed fine without it. I can add it back, if necessary.

[mdrichardson]

Match conditions and eTags changed quite a bit and I'm not 100% confident that I implemented this correctly. I tried some other approaches and this was the one that made all of our tests pass. Please review this part closely.

[mdrichardson]

Converting back to draft. Looks like the azure-storage-blob package adds some quotes to some of the blob references, which breaks backwards-compat. I partially handled this here, but am fixing elsewhere.

Edit: Fixed. I was trying to encode the blob names ('emulator/users/d4c5e82a-16f9-4709-89d6-b0b4cc0255e2') like the other SDKs do, but calling jsonpickler.encode() on it results in extra quotes being added, like: ("'emulator/users/d4c5e82a-16f9-4709-89d6-b0b4cc0255e2'").