Prior to this commit, `DataSourceJmxConfiguration` with tomcat
`DataSource`, it can only find `DataSourceProxy` if the given
`DataSource` is a direct child of it. Since it uses `instanceof`, it
could not find `DataSourceProxy` if the `DataSource` is
wrapped(delegated) or proxied.
This is because `DataSourceProxy#unwrap()` always returns null; thus
cannot use this method to directly obtain `DataSourceProxy`.
In this commit, updated the check logic to perform the best effort to
retrieve `DataSourceProxy`. If given `DataSource` is wrapped or proxied
by spring, tries to unwrap or get target datasource recursively to find
`DataSourceProxy`.
See gh-15206
26f9a92837