Upgrade azure_identity and azure_core to latest 0.20 version

[cool-mist]

Is your feature request related to a problem? Please describe.
A lot of other sdks for rust have started using the 0.20 versions for azure_identity and azure_core. Because of the way cargo handles conflicts, when a project includes both the azure-kusto-XXX and some other sdk that uses the 0.20 versions, compilation fails.

Describe the solution you'd like
Upgrade the kusto rust sdks to 0.20 versions of azure_identity and azure_core

Describe alternatives you've considered
None

Additional context
NA

[AsafMah]

For now we are blocked with Azure/azure-sdk-for-rust#1659

[AsafMah]

I saw that 0.2.1 was released, I'll try to get on it.

[AsafMah]

Seems that it's still not there in 0.21.0, sorry