Add PCU operations support

[toptobes]

STATUS: Currently all of the implementation code is written and in theory working, but is not tested as of yet (no actual access to PCU stuff yet). Also a lot of minor TODOs to come back to.

Adds support for the following:

• pcu_group data source
• pcu_groups data source
• pcu_group_associations data source
• resolve_datacenter function (warning: requires terraform v1.8+)
• pcu_group resource
• pcu_group_association resource

Had to comment out the implementations of a few other resources/data sources as the modified astra-go-client used in this branch has unintended breaking changes.

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TODOs before merging

• Inconsistent return for cloud provider value (observed AZURE vs Azure coming back from API?) -> should sanitize the case of return values?
• Fix non-backwards-compatible changes in astra-go-client on related PR

[Copilot]

Pull Request Overview

This PR adds comprehensive support for PCU (Provisioned Capacity Units) operations, enabling users to manage dedicated compute capacity for databases through Terraform. The implementation includes data sources for querying PCU groups and associations, resources for managing them, and a provider function to simplify datacenter ID resolution.

Key changes:

• Adds PCU group management resources and data sources for provisioning and querying dedicated compute capacity
• Introduces a resolve_datacenter function to simplify datacenter ID lookups from database resources
• Updates test infrastructure to properly export environment variables for acceptance tests

Reviewed Changes

Copilot reviewed 32 out of 34 changed files in this pull request and generated 7 comments.

Show a summary per file

File	Description
test/run_tests.sh	Exports TF_ACC environment variable to enable acceptance tests
internal/provider/validators.go	Adds Int32 validator for greater-than-or-equal-to comparisons
internal/provider/utils_pcu.go	Implements core PCU service interfaces and API interaction logic
internal/provider/util_terraform.go	Adds helper functions for Terraform attribute merging and HTTP response handling
internal/provider/util_misc.go	Adds generic utility functions for nil handling and type conversions
internal/provider/types_pcus.go	Defines PCU data models and schema attribute builders
internal/provider/resource_table.go	Updates import order (cosmetic change)
internal/provider/resource_pcu_group_test.go	Adds acceptance tests for PCU group lifecycle
internal/provider/resource_pcu_group_assocation.go	Implements PCU group association resource with transfer support
internal/provider/resource_pcu_group.go	Implements PCU group resource with park/unpark functionality
internal/provider/resource_database.go	Updates comments from "All" to "FindById"
internal/provider/provider_framework_test.go	Adds test helper for creating Astra client
internal/provider/provider_framework.go	Registers new PCU data sources, resources, and functions
internal/provider/function_resolve_datacenter.go	Implements datacenter ID resolution function
internal/provider/data_source_pcu_groups.go	Implements data source for listing PCU groups
internal/provider/data_source_pcu_group_associations.go	Implements data source for PCU group associations
internal/provider/data_source_pcu_group.go	Implements data source for single PCU group lookup
go.mod	Updates Go version and dependency versions
examples/ and docs/ files	Adds documentation and examples for new PCU features

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