chore: (DevOps) Improve spec-update workflow

[Jonas-Isr]

Context

• https://github.com/SAP/ai-sdk-java-backlog/issues/361

This PR improves the behaviour of our spec update workflow.

Background
We had the case before where a branch on the grounding repo was breaking the spec (resulting in a failed SDK check) but then simply committed something onto the branch without any spec changes. This led to the SDK check turning green, as the check only considered the most recent commit which did not have any spec changes and therefor skipped generation on our side.

To solve this, the workflow now checks for previous runs (from the same feature branch, using the run-name option as a filter) when no spec changes are detected. The logic when no spec changes detected is as follows:

• if there is no previous run, current run succeeds,
• if there is a previous run, current run succeeds if and only if the previous run succeeded.

Refer to the following 2 branches on the orch-repo for tests of this workflow.

• https://github.tools.sap/AI/llm-orchestration/pull/2351
• https://github.tools.sap/AI/llm-orchestration/pull/2352

Feature scope:

• improve workflow
• test it with orchestration spec changes

Definition of Done

• Functionality scope stated & covered
• Tests cover the scope above
• Error handling created / updated & covered by the tests above
• Aligned changes with the JavaScript SDK
• Documentation updated
• Release notes updated

[CharlesDuboisSAP]

The test runs look good. The weekly update should work this weekend