Grails 7: Make groovy-joint-workflow work as intended

[jamesfredley]

These changes have been completed on https://github.com/grails/grails-core/pull/13681

• Removed the mavenLocal() repository from the build configuration, as it was only required for the groovy-joint-workflow GitHub workflow.
• Updated the groovy-joint-workflow to dynamically add mavenLocal() to the build file at runtime, ensuring it is only used in the relevant workflow without affecting other builds.
• Simplify the build by removing the use of CI_GROOVY_VERSION enviroment var and override the project property groovyVersion with a command line property assignment instead.
• Use publishToMavenLocal instead of install when building Groovy as Grails will try to load the Groovy libraries from mavenLocal().

With these changes the groovy-joint-worflow actually uses the built Groovy libraries when building Grails.

They need to be completed on the following repos:

https://github.com/grails/grails-data-mapping https://github.com/grails/grails-gsp https://github.com/grails/grails-async https://github.com/grails/gorm-neo4j https://github.com/grails/gorm-mongodb https://github.com/grails/gorm-hibernate5

Already completed on: https://github.com/grails/grails-views https://github.com/grails/grails-testing-support