Implement Azure Blob Store

[amankrx]

Description

This PR implements the Azure Blob Store implementation and closely aligns with the AWS S3 implementation.
This utilizes the azure_sdk libraries (azure_core, azure_storage, and azure_storage_blobs). The libraries are still unofficial and being developed, so we should be mindful of any breaking changes in the future.

Apart from that, I started my development by first creating a POC: https://gist.github.com/amankrx/45e7d2a6ed935aa13dda0318681af2ad
This POC tests the get and upload blobs with all the default features disabled for Azure SDK. This creates a custom HttpClient with manually signing the requests to perform the transactions.

Fixes #1542
/claim #1542

Type of change

Please delete options that aren't relevant.

• New feature (non-breaking change which adds functionality)
• This change requires a documentation update

How Has This Been Tested?

I tested it locally using the bazel test command with the azure_blob_backend.json5 file, configured to use the actual blob storage. To test this locally, you should set the environment variable AZURE_STORAGE_KEY as the access key. Additionally, I created a test suite to cover both individual happy paths and error scenarios.

Checklist

• Updated documentation if needed
• Tests added/amended
• Local testing completed
• bazel test //... passes locally
• PR is contained in a single commit, using git amend see some docs

---

This change is 

[CLAassistant]

All committers have signed the CLA.

[amankrx]

I have updated the PR with the latest changes and have verified that it works locally.
Awaiting review from @MarcusSorealheis @aaronmondal

[amankrx]

Any updates here?

[aaronmondal]

Looks pretty good already. One thing I'm wondering is what happened to the buffer logic from the S3 implementation. Was that not usable here or did it have other issues?

Regarding the code, there seems to be quite a lot of duplication going on though. WDYT about something roughly like this?

+---------------Current Architecture-----+  +------Refactored Architecture----+
|                                        |  |                                 |
|       +----------------------------+   |  | +----------------------------+  |
|       |      StoreDriver Trait     |   |  | |      StoreDriver Trait     |  |
|       |  Common interface for all  |   |  | |  Common interface for all  |  |
|       |         storage            |   |  | |          storage           |  |
|       +----------------------------+   |  | +----------------------------+  |
|                    |                   |  |                |                |
|              implemented by            |  |          implemented by         |
|                    |                   |  |                |                |
|                    v                   |  |                v                |
| +----------+ +----------+ +----------+ |  | +-----------------------------+ |
| |          | |          | |          | |  | |  GenericCloudStore<P,NowFn> | |
| |  S3Store | |AzureStore| | GcsStore | |  | |   Common implementation     | |
| |          | |          | |          | |  | |with optimized critical paths| |
| +----------+ +----------+ +----------+ |  | +-----------------------------+ |
|                                        |  |                |                |
+----------------------------------------+  |              uses               |
                                            |                |                |
                                            |                v                |
                                            | +----------------------------+  |
                                            | |  CloudStorageProvider Trait|  |
                                            | |    Minimal provider-       |  |
                                            | |    specific operations     |  |
                                            | +----------------------------+  |
                                            |                |                |
                                            |          implemented by         |
                                            |                |                |
                                            |      +---------+---------+      |
                                            |      |         |         |      |
                                            |      v         v         v      |
                                            | +------+   +------+   +------+  |
                                            | |  S3  |   |Azure |   | GCS  |  |
                                            | +------+   +------+   +------+  |
                                            |                                 |
                                            +---------------------------------+

There are other parts that look very duplicated among the now 3 store implementations like the object path logic and the request transformations across the stores.

+@jhpratt

Reviewable status: 0 of 2 LGTMs obtained, and 0 of 10 files reviewed (waiting on @jhpratt)

[amankrx]

Exactly! This is something that I had planned as well. But it needs some restructuring, that was out of scope for this PR atleast. We can maybe create a separate PR that handles the GenericCloudStore. This would minimize a lot of duplication.

Reviewable status: 0 of 2 LGTMs obtained, and 0 of 10 files reviewed (waiting on @jhpratt)