Enhance cloudstack_disk_offering resource and datasource

[bddvlpr]

Adds a bunch of missing parameters to the disk offering resource. Initialized the data source for it while I was at it.

Tested on simulator.

[Copilot]

Pull request overview

This PR enhances the cloudstack_disk_offering Terraform resource to support additional CloudStack disk-offering parameters and completes the CRUD implementation, while also introducing a new cloudstack_disk_offering data source (plus docs and acceptance tests) so disk offerings can be discovered and referenced by other resources.

Changes:

• Expanded cloudstack_disk_offering resource schema (custom sizing, storage/provisioning type, tags, display flag) and implemented Read/Update/Delete + Importer.
• Added cloudstack_disk_offering data source with filter-based selection and acceptance tests.
• Updated/added website documentation for the resource and data source.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
website/docs/r/disk_offering.html.markdown	Documents the expanded disk offering resource arguments and attributes.
website/docs/d/disk_offering.html.markdown	Adds documentation for the new disk offering data source.
cloudstack/resource_cloudstack_disk_offering.go	Implements full disk offering resource CRUD/import and adds missing schema parameters.
cloudstack/resource_cloudstack_disk_offering_test.go	Adds acceptance tests for disk offering resource scenarios (basic/customized/update).
cloudstack/provider.go	Registers the new disk offering data source with the provider.
cloudstack/data_source_cloudstack_disk_offering.go	Implements the disk offering data source and filter logic.
cloudstack/data_source_cloudstack_disk_offering_test.go	Adds an acceptance test validating the disk offering data source against a created resource.

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