Combined maven pipeline configs from WRS and Java Common into a new common template

Added new maven.gitlab-ci.yml to combine project specific templates used by HR Java Common and WRS projects

Also see MRs for updated projects: WRS: https://gitlab.developers.cam.ac.uk/uis/devops/hr/wr/wrs-webapp/-/merge_requests/35 Java Common: https://gitlab.developers.cam.ac.uk/uis/devops/hr/java-common/java-common/-/merge_requests/24

To allow for the job differences between the 2 projects, the following variables are set in the projects to disable unneeded features: WRS, includes:

• maven:verify
• retrieves GitLab Access tokens
• maven:build disabled with: MAVEN_BUILD_DISABLED: "1"

Java Common, includes:

• maven:verify
• maven:build
• does not retrieve GitLab Access tokens, feature disabled with: MAVEN_ACCESS_TOKENS_DISABLED: "1"