Setup DataSource early to take advantage of AutoConfiguration

Its looks to me like we can have an AutoConfiguration that will work with both Grails or Spring Boot/Micronaut.

- If we use AutoConfiguration to setup the DataSource early using the then all the other AutoConfiguration that depend on datasource can be taken advantage of.
- as it stands no in grails-plugin, its setup to late in the process for the other Autoconfigurations to get picked up
- grails HibernateDatastoreConnectionSourcesRegistrar.postProcessBeanDefinitionRegistry sets up the dataSource but checks for existing first.
- in order for other spring boot Autoconfigure (such as actuator metrics) to get picked up then datasource needs to be setup early.

so instead of using HibernateDatastoreSpringInitializer it can autoconfigure the dataSourceConnectionSourceFactory(CachedDataSourceConnectionSourceFactory)
and the Datasource early (which looks like it should be a factory based on dataSourceConnectionSourceFactory)

Start by reading grails-plugin's HibernateDatastoreConnectionSourcesRegistrar and HibernateDatastoreSpringInitializer, along with CachedDataSourceConnectionSourceFactory. Trace when the DataSource and dataSourceConnectionSourceFactory are created relative to AutoConfiguration. Done means the DataSource is available early enough for other datasource-dependent AutoConfiguration while supporting Grails and Spring Boot/Micronaut.

Written by the indexing model from the issue text.