Add integration test for Batchx509SVID RPC

[valverdethiago]

Pull Request check list

• Commit conforms to CONTRIBUTING.md?
• Proper tests/regressions included?
• Documentation updated?

Provides a way to verify the operation of Batchx509SVID RPC.

Description of change
This PR introduces an automated integration test for the Batchx509SVID RPC in Open Source SPIRE. The new test script ensures the continuous operation of this RPC by verifying its functionality in a controlled environment. This enhancement addresses the previously identified gap in automated testing, thereby improving the reliability and stability of the SPIRE project by ensuring that the Batchx509SVID RPC performs as expected over time.

Which issue this PR fixes
Fixes 5401

[amoore877]

this step as-is verifies that the entries exist, as created in the prior step.

however, neither this suite nor this step test the BatchNewX509SVID API

[valverdethiago]

As I talked with @zmt the batch API is called internally when we add a single entry or create a batch operation as the test is already doing. The check for the existence of the entry fullfils the purpose of the task case if they were created in a batch operation and actually exist the operation is working as expected, right?

[amoore877]

what I believe you're detailing is Batch Entry Create, not Batch X509 SVID.

if the former, then the test needs to be re-named and the README updated

if the intention is to cover the latter, then comment still stands- this test as-is is not covering either explicit usage of that API or implicit usage by the running agent (which https://github.com/spiffe/spire/blob/main/test/integration/suites/fetch-x509-svids/05-fetch-x509-svids may already be doing)