Create jenkins pipeline for wallet backend release

[gouthamp-stellar]

Create a jenkins pipeline that builds a docker image using a release branch and pushes it to docker hub to https://hub.docker.com/r/stellar/wallet-backend.
Tag the docker image with the release version number.

For more details, take a look at the wallet backend release plan doc, particularly step 3: https://docs.google.com/document/d/1aY02L49GU4HXo5KUiBi3QAYJIFZiyuOeiPVt0tcLXmA/edit?tab=t.0