Tasks about updating links in spring.io

[backwind1233]

Context
We should update the link of https://spring.io/projects/spring-cloud-azure#samples when sample is adjusted.
Now the link in https://spring.io/projects/spring-cloud-azure#samples is azure-spring-boot-samples.

Task

1. Rename folder name from aad to azure active directory
   now folder name aad is not consistant with offical doc, may be confusing.
   • rename folder @backwind1233
   • Update spring reference yaml
   • update links in samples, azure-sdk-for-java,azure-dev-docs-pr

• Update sample links in spring.io

[stliu]

@chenrujun I'm reassigning this to you since this is part of our samples visibility tasks

[saragluna]

Closing this issue now.