Consolidate grails-data-graphql and grails-data-neo4j into grails-data-mapping

[jamesfredley]

Consolidate grails-data-graphql 4.0.x branch and grails-data-neo4j 8.2.x branch into grails-data-mapping.

Neither of these have been updated for Grails 7, so they will not be built for now, but are being brough over so they can be updated at a later time.

Migrate issues:
https://github.com/grails/grails-data-graphql/issues
https://github.com/grails/grails-data-neo4j/issues

Update default branch with readme like:
https://github.com/grails/grails-functional-tests

Review open PRs:
Almost entirely dependabot, which will be ignored.

git remote add neo4j git@github.com:grails/grails-data-neo4j.git
git fetch neo4j 
git merge -s ours --no-commit --allow-unrelated-histories neo4j/8.2.x
git read-tree --prefix=neo4j/ -u neo4j/8.2.x
git commit -m "Imported grails-data-neo4j"

git remote add graphql git@github.com:grails/grails-data-graphql.git
git fetch graphql
git merge -s ours --no-commit --allow-unrelated-histories graphql/4.0.x
git read-tree --prefix=graphql/ -u graphql/4.0.x
git commit -m "Imported grails-data-graphql"