Default Hibernate DDL auto to none with Flyway/Liquibase

This commit adds a strategy interface to specific if a given DataSource
has its schema managed. The Hibernate auto-configuration uses it to set
it to "none" if a mechanism to initialize the DataSource is
found and "create-drop" otherwise.

Both Flyway and Liquibase implements that strategy interface and
register it in the context accordingly.

Closes gh-9262

spring-boot-samples/spring-boot-sample-liquibase/src/main/resources/application.properties

@@ -1,5 +1,3 @@
 management.security.enabled=false
 
-spring.jpa.hibernate.ddl-auto=none
-
 spring.h2.console.enabled=true