Adds spring.datasource.lazy-connection property to enable Lazy DataSource support

[nosan]

This commit adds spring.datasource.lazy-connection property into a DataSourceProperties class to enable a LazyConnectionDataSourceBeanPostProcessor. BeanPostProcessor wraps an auto-configured DataSource in a LazyConnectionDataSourceProxy. It will be added only if a
spring.datasource.lazy-connection property has true and a LazyConnectionDataSourceProxy
class is present. The default value of the spring.datasource.lazy-connection property is false, which means a lazy-connection feature is disabled by default.

see gh-15480

Note! LazyConnectionDataSourceBeanPostProcessor it is being invoked after DataSourceInitializerPostProcessor (I'm not sure that is the right behaviour)

Thanks in advance.

[wilkinsona]

Thanks for the PR. I'm not sure that a bean post-processor is the best way to implement this. If there's a second auto-configured DataSource, it will also be wrapped in a LazyConnectionDataSourceProxy and I don't think it should be.

I think we'll need to do something that means we can be certain that it's only the auto-configured data source that will be wrapped. We also need to make a decision about whether or not the wrapping should be enabled by default. Let's use #15480 to do that. Thanks anyway.