Added AzureStorageCredentialsService controller service interface
with 2 implementations:
- AzureStorageCredentialsControllerService: holds the credential properties
(account name, account key, sas token)
- AzureStorageCredentialsControllerServiceLookup: can be used to dynamically
look up another AzureStorageCredentialsService (similar to
DBCPConnectionPoolLookup)
The controller service can be used by the Azure Storage processors:
{List|Fetch|Put|Delete}AzureBlobStorage, {Get|Put}AzureQueueStorage
NIFI-6550: Review changes.
NIFI-6550: Review changes #2.
This closes#3742.
Signed-off-by: Koji Kawamura <ijokarumawak@apache.org>