add "create path" operation (files only for now) to Azure Storage data_lake (using Pipeline architecture)

[thovoll]

This adds create_path operation (files only for now) to the data_lake crate using the pipeline architecture and adds examples.

Issue #356

[thovoll]

Doesn't compile yet

[thovoll]

Will add integration tests separately: #372

[thovoll]

e2e test works now, manually validated with the following environment variables set to valid values:
AZURE_TENANT_ID
AZURE_CLIENT_ID
AZURE_CLIENT_SECRET
ADSL_STORAGE_ACCOUNT
ADSL_STORAGE_MASTER_KEY (for operations other than 'create path')
Command: cargo test --features test_e2e -p azure_storage --test data_lake -- --nocapture

The DefaultCredential ends up using EnvironmentCredential which ends up using ClientSecretCredential.

[rylev]

Looks good! Sorry for not getting a review on this sooner - we've been focused on cosmos. I'd like to try to adopt the mock testing framework as I noted in one of the comments before we merge this.

[rylev]

♥ Thanks for taking the time to work on this! There are some nits I found in the review, but nothing blocking. I'm going to merge this, and we can address the nits in a follow up.

[thovoll]

Thanks @rylev! New branch here, will raise PR later: https://github.com/thovoll/azure-sdk-for-rust/commits/data_lake/create_path_2

[thovoll]

Follow-up PRs: #451 and #491