Migrate Kusto test utilities and integration helpers off legacy kusto client

[mkeesey]

Context

Several test utilities and integration helpers still use the legacy root github.com/Azure/azure-kusto-go/kusto client. These are not the main production dependency drivers, but they will keep legacy imports around after production paths migrate.

Files

• pkg/testutils/kql_verify.go
• pkg/testutils/integration_test.go
• pkg/testutils/kustainer/kustainer.go

Current legacy usage

• Creates Kusto clients against kustainer/local ADX with kusto.NewConnectionStringBuilder and kusto.New.
• Executes management commands and queries with client.Mgmt / client.Query.
• Builds statements with legacy kusto/kql.
• Reads results with NextRowOrError and ToStruct.

Helper behaviors to preserve

• Verify table existence.
• Verify function existence and retrieve function metadata.
• Verify table row counts.
• Verify table schemas via getschema.
• Create volatile databases in kustainer.
• Alter ingestion batching policy.
• Query integration-test health metrics.

Acceptance criteria

• Test utility packages no longer import github.com/Azure/azure-kusto-go/kusto... packages.
• Existing integration helper behavior remains available for tests.
• Kustainer/local endpoint support remains working.