feat: add azblob storage backend with opendal

[George-Miao]

This PR adds azure blob support with OpenDAL. Currently we are still waiting for unftp-sbe-opendal to release, so it's a git dependency for now. Azure blob can be used as an example for future implementation of storages backed by OpenDAL.

I'm not sure how should we organize the naming (arg, env) for services provided by OpenDAL though.

Closes #183

[Xuanwo]

Mostly look good to me from my view, great work!

[hannesdejager]

@George-Miao Great stuff! Thank you! I’ll have a look over the week-end. We’ll need the unftp-sbe-opendal to release before merge.

[Xuanwo]

Hi, unftp-sbe-opendal v0.0.1 has been released: https://crates.io/crates/unftp-sbe-opendal

Please check it out.

[George-Miao]

I have updated the dependency

[hannesdejager]

We have compilation errors when the azblob feature is switched off. You will want only enable the code if this feature is on.

We should also add this feature to the different builds in the github actions file.

[hannesdejager]

You can add unftp-sbe-opendal to the Known storage back-ends list at https://github.com/bolcom/unFTP/blob/master/docs/libunftp/README.md

[George-Miao]

We have compilation errors when the azblob feature is switched off.

unftp_sbe_gcs will also cause the compilation error when default features are turned off. Is that on purpose?

[hannesdejager]

@George-Miao I think there was a ticket to fix that

[hannesdejager]

@George-Miao looking much better only the gnu build is failing now