Generate api.md for Java module

[weidongxu-microsoft]

Add --renderer=markdown option to https://github.com/Azure/azure-sdk-tools/tree/main/src/java/apiview-java-processor

• Add direct Markdown output to Java APIView processor azure-sdk-tools#16809

---

Integration

• integrate into SDK Generation pipeline
• command to generate api.md when user does not use the pipeline (this is what Python does -- another alternative is to have agent on PR to regen the api.md and commit, if not match)

---

Question

• How to build the apiview-java-processor, given it currently in the tools repo? Should we move it into SDK repo? Or upload the build to devfeed?

[weidongxu-microsoft]

sample output
https://github.com/Azure/azure-sdk-for-java/pull/50226/changes