[EventHubs] update vendor storage blob code

[yunhaoling]

trying to resolve issues: #16192
use the storage-blob version v12.7.1: https://github.com/Azure/azure-sdk-for-python/tree/azure-storage-blob_12.7.1, commit id: e8edeb8

[yunhaoling]

/azp run python - eventhub - tests

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Azure Pipelines successfully started running 1 pipeline(s).

[yunhaoling]

/azp run python - eventhub - tests

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Azure Pipelines successfully started running 1 pipeline(s).

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[yunhaoling]

/azp run python - eventhub - tests

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Azure Pipelines successfully started running 1 pipeline(s).

[swathipil]

lgtm

[annatisch]

Given that there's been some updates to error handling - do any of out live tests deal with errors raised from Storage? It shouldn't be an issue, but would be nice to know we have coverage :)

[yunhaoling]

nope, we don't have tests covering storage errors as for most blob storage errors, our sdk simply bubble up or ignore them.

The only errors we care about are ResourceModifiedError, ResourceExistsError which are treated as OwnershipLostError:

azure-sdk-for-python/sdk/eventhub/azure-eventhub-checkpointstoreblob/azure/eventhub/extensions/checkpointstoreblob/_blobstoragecs.py

Lines 163 to 173 in f0697ff

	except (ResourceModifiedError, ResourceExistsError):
	logger.info(
	"EventProcessor instance %r of namespace %r eventhub %r consumer group %r "
	"lost ownership to partition %r",
	owner_id,
	fully_qualified_namespace,
	eventhub_name,
	consumer_group,
	partition_id,
	)
	raise OwnershipLostError()

I don't think we need to cover all of the blob storage errors now based on our current "bubble up or ignore" approach. but I'm always open to adding new tests if needed :P

[annatisch]

A couple of questions but generally looks good to me.