COG-Azure plugin- support Anonymous access

[dromagnoli]

It would be great to create unit tests not using internal blobs.
This wil require accessing public data.
Sentinel 2 has many of them but they require a Token.
Need to figure out how to access BLOB via SAS Token.

However, the only documentation available around about Azure is for v12 of the library which is a lot different with respect to v11 that we currently use. Need sme investigation,