[FEATURE REQ] Add CredentialBuilderFactory for WorkloadIdentityCredential

[rujche]

In this page: https://github.com/Azure/azure-sdk-for-java/tree/main/sdk/spring/spring-cloud-azure-core/src/main/java/com/azure/spring/cloud/core/implementation/factory/credential

We already have CredentialBuilderFactory for kinds of TokenCredential, now WorkloadIdentityCredential has been released, we should add TokenCredential for WorkloadIdentityCredential.

[Netyyyy]

We will consider this feature later.