Fix ASN and Hostname list items

[Cyb3r-Jak3]

Fixes issues preventing usage of asn or hostname as cloudflare_list_item resources.

ASN fails because the ASN number is provider as an int and getSearchTerm was typecasting as a string.

Hostname fails because it is hostname is a block and not a string.

Adds unit tests for both kinds of list_item to prevent future issues.

[github-actions]

changelog detected ✅

[jacobbednarz]

thanks! acceptance tests look good

TF_ACC=1 go test ./internal/sdkv2provider -v -run "^TestAccCloudflareListItem_" -count 1 -timeout 120m -parallel 1

=== RUN   TestAccCloudflareListItem_Basic
--- PASS: TestAccCloudflareListItem_Basic (16.06s)
=== RUN   TestAccCloudflareListItem_MultipleItems
--- PASS: TestAccCloudflareListItem_MultipleItems (20.58s)
=== RUN   TestAccCloudflareListItem_Update
--- PASS: TestAccCloudflareListItem_Update (22.94s)
=== RUN   TestAccCloudflareListItem_BadListItemType
--- PASS: TestAccCloudflareListItem_BadListItemType (5.56s)
=== RUN   TestAccCloudflareListItem_ASN
--- PASS: TestAccCloudflareListItem_ASN (13.26s)
=== RUN   TestAccCloudflareListItem_Hostname
--- PASS: TestAccCloudflareListItem_Hostname (13.36s)
PASS
ok  	github.com/cloudflare/terraform-provider-cloudflare/internal/sdkv2provider	92.969s

[github-actions]

This functionality has been released in v4.20.0 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!