Integration DataSource initialization should back off without spring-boot-sql

[wilkinsona]

See #46240 for a little bit of background. We can also remove the implementation dependency on spring-boot-sql as the optional dependency on spring-boot-jdbc is sufficient.

[wilkinsona]

We can also remove the implementation dependency on spring-boot-sql as the optional dependency on spring-boot-jdbc is sufficient

There's a bit more to this as the auto-configuration currently assumes that spring-boot-sql will always be present. It needs to be reworked slightly so that spring-boot-sql can become optional (through spring-boot-jdbc) and backs off in its absence.