[Storage] az storage blob upload: make --name optional

[calvinhzy]

Description

Previously, the --name parameter is required even when the file path has been passed. For customers' convenience, it can be optional. This PR is to match #19553 in the main repo.

Testing Guide

Previously -n is required
az storage blob upload -f {file-path} -c {container-name} -n {blob-name}
Now the name would be inferred from the file-path
az storage blob upload -f {file-path} -c {container-name}

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[yonzhan]

Storage