[MRELEASE-839]: Unable to supply tag to release for release:perform

[edwardUL99]

Following this checklist to help us incorporate your contribution quickly and easily:

• [x] Make sure there is a JIRA issue filed for the change (usually before you start working on it). Trivial changes like typos do not require a JIRA issue. Your pull request should address just this issue, without pulling in other changes.
• [X] Each commit in the pull request should have a meaningful subject line and body.
• [X] Format the pull request title like [MJAVADOC-XXX] - Fixes bug in ApproximateQuantiles, where you replace MJAVADOC-XXX with the appropriate JIRA issue. Best practice is to use the JIRA issue title in the pull request title and in the first line of the commit message.
• [X] Write a pull request description that is detailed enough to understand what the pull request does, how, and why.
• [X] Run mvn clean verify -Prun-its to make sure basic checks pass. A more thorough check will be performed on your pull request automatically.

If your pull request is about ~20 lines of code you don't need to sign an Individual Contributor License Agreement if you are unsure please ask on the developers list.

To make clear that you license your contribution under the Apache License Version 2.0, January 2004 you have to acknowledge this by using the following check-box.

• [X] I hereby declare this contribution to be licenced under the Apache License Version 2.0, January 2004

• [x] In any other case, please file an Apache Individual Contributor License Agreement.

This PR introduces a fix which allows a tag to be supplied either using a -Dtag=<tag> flag or passing the tag into the <configuration><tag>tag</tag></configuration> section of the release plugin in the pom. The PerformReleasePojo previously incorrectly extended AbstractReleaseMojo where it now extends AbstractScmReleaseMojo. This required some small changes to the unit tests where I updated the stub files to correct a NPE error and to also assert that the ScmReleaseLabel was being populated correctly. I also added a directory MRELEASE-839 under it/projects/perform which contains the integration test for this issue.

From the Jira, the command to get the fixed changes is:

mvn org.apache.maven.plugins:maven-release-plugin:3.0.0-M7-SNAPSHOT:perform -DconnectionUrl=scm:git:https://gitlab.com/fake/r365-autoconfig.git -Dtag=0.1.14 -DuseReleaseProfile=false

Replacing the connectionUrl with correct SCM and required tag. I have tested that it works with both localCheckout set to true and false