d/azurerm_eventgrid_system_topic: New data source

[aristosvo]

Fixes #13846

Acceptance Tests:

❯ go install && make acctests SERVICE='eventgrid' TESTARGS='-run=TestAccEventGridSystemTopicDataSource_'
==> Checking that code complies with gofmt requirements...
==> Checking that Custom Timeouts are used...
==> Checking that acceptance test packages are used...
TF_ACC=1 go test -v ./internal/services/eventgrid -run=TestAccEventGridSystemTopicDataSource_ -timeout 180m -ldflags="-X=github.com/hashicorp/terraform-provider-azurerm/version.ProviderVersion=acc"
=== RUN   TestAccEventGridSystemTopicDataSource_complete
=== PAUSE TestAccEventGridSystemTopicDataSource_complete
=== RUN   TestAccEventGridSystemTopicDataSource_basicWithSystemManagedIdentity
=== PAUSE TestAccEventGridSystemTopicDataSource_basicWithSystemManagedIdentity
=== RUN   TestAccEventGridSystemTopicDataSource_basicWithUserAssignedManagedIdentity
=== PAUSE TestAccEventGridSystemTopicDataSource_basicWithUserAssignedManagedIdentity
=== CONT  TestAccEventGridSystemTopicDataSource_complete
=== CONT  TestAccEventGridSystemTopicDataSource_basicWithUserAssignedManagedIdentity
=== CONT  TestAccEventGridSystemTopicDataSource_basicWithSystemManagedIdentity
--- PASS: TestAccEventGridSystemTopicDataSource_complete (118.19s)
--- PASS: TestAccEventGridSystemTopicDataSource_basicWithUserAssignedManagedIdentity (126.96s)
--- PASS: TestAccEventGridSystemTopicDataSource_basicWithSystemManagedIdentity (129.14s)
PASS
ok      github.com/hashicorp/terraform-provider-azurerm/internal/services/eventgrid     130.667s

[katbyte]

Thanks @aristosvo - LGTM 💯

[github-actions]

This functionality has been released in v2.83.0 of the Terraform 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!

[github-actions]

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