Previously, the auto-configuration for DataSource initialization and
the properties used to configure it were part of the general
DataSource auto-configuration and properties.

This commit moves the auto-configuration of DataSource initialization
out into a separate top-level auto-configuration class. Similarly,
the properties for configuring DataSource initialization have been
moved from `spring.datasource.*` into `spring.sql.init.*`.

The old initialization-related `spring.datasource.*` properties have
been deprecated but can still be used. When they are used, they new,
separate initialization auto-configuration will back off. In other
words, the initialization related `spring.datasource.*` properties
and the `spring.sql.init.*` properties cannot be used in combination.

Closes gh-25323