Promote dapr-sdk-workflows from Alpha -> Stable

[cicoyle]

In Dapr, workflows went stable in v1.15. We should make dapr-sdk-workflows stable to align with upstream runtime

Steps to make it stable:

1. We should investigate what all is missing to make workflows stable from a Java sdk perspective and make it happen.
2. Property alignment: Update dapr.sdk.alpha.version to dapr.sdk.version for workflows
3. See about any script updates in the update_sdk_version.sh file to make sure we dont break our release automation
4. Documentation updates