TPT-2038: Refactor for bucket migration

[zliang-akamai]

Description

Refactor the helper function that gets OBJ keys from framework data model to be shared among multiple framework models who implements the interface.

Test

make PKG_NAME="obj" test-int

[Copilot]

Pull request overview

Refactors Object Storage (OBJ) key/identifier access in preparation for bucket migration by extracting common “bucket context” accessors and centralizing Object Storage key resolution.

Changes:

• Added BucketAccessor interface and a shared GetObjectStorageKeys resolver for OBJ framework resources.
• Updated OBJ resource model to expose RegionOrCluster, BucketLabel, and ObjectStorageKeys accessors (and removed the prior model-specific key-resolution method).
• Minor schema/model refactors in objbucket to support consistent bucket attribute handling.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
linode/objbucket/framework_models.go	Adds helper accessors on the framework bucket model (RegionOrCluster, BucketLabel).
linode/objbucket/framework_datasource_schema.go	Reorders/organizes datasource attributes (no functional behavior change expected).
linode/obj/helpers.go	Switches to the new package-level GetObjectStorageKeys resolver.
linode/obj/framework_resource.go	Updates logging to use the renamed RegionOrCluster model method.
linode/obj/framework_models.go	Renames GetRegionOrCluster → RegionOrCluster; adds ObjectStorageKeys and BucketLabel; removes model-scoped key resolution.
linode/obj/bucket_accessor.go	Introduces BucketAccessor + centralized GetObjectStorageKeys implementation.

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[lgarber-akamai]

Looks great and tests are passing locally, nice work!