Add support for specifying storage pool with name or partial url.

[modular-magician]

Add support for specifying storage pool with name or partial url.
Since storage pool is not a resource in Terraform, we need a new method for expanding given storage pool name or partial URL.
Added for both Disk and Instance.

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compute: add support for specifying storage pool with name or partial url

Derived from GoogleCloudPlatform/magic-modules#12111