Don't set items for lists when not needed

[Cyb3r-Jak3]

Fixes #4469

Before, the cloudflare_list resource would always read the items from a list, even if they were not configured. With this change, items from the list are not read if there are none in the model. Similar to the SDKV2 resource.

The best way to test this is the list_item tests, as they will fail without this change.

[github-actions]

changelog detected ✅

[jacobbednarz]

tests are passing

TF_ACC=1 go test ./internal/framework/service/list/ -run "^TestAcc" -count 1 -v
=== RUN   TestAccCloudflareList_Exists
--- PASS: TestAccCloudflareList_Exists (2.56s)
=== RUN   TestAccCloudflareList_UpdateDescription
--- PASS: TestAccCloudflareList_UpdateDescription (6.02s)
=== RUN   TestAccCloudflareList_Update
--- PASS: TestAccCloudflareList_Update (30.98s)
=== RUN   TestAccCloudflareList_UpdateIgnoreIPOrdering
--- PASS: TestAccCloudflareList_UpdateIgnoreIPOrdering (5.26s)
=== RUN   TestAccCloudflareList_RemoveInlineConfig
--- PASS: TestAccCloudflareList_RemoveInlineConfig (10.54s)
PASS
ok  	github.com/cloudflare/terraform-provider-cloudflare/internal/framework/service/list	56.562s

[github-actions]

This functionality has been released in v4.46.0 of the Terraform Cloudflare Provider.

Please see the Terraform documentation on provider versioning or reach out if you need any assistance upgrading.

For further feature requests or bug reports with this functionality, please create a new GitHub issue following the template. Thank you!