Add auto-configuration for JdbcClient

[mhalbritter]

Spring Framework 6.1 introduces the new JdbcClient. We should add an auto-configuration for it.

@jhoeller suggested something like this:

@Configuration(proxyBeanMethods = false)
@ConditionalOnSingleCandidate(NamedParameterJdbcTemplate.class)
@ConditionalOnMissingBean(JdbcClient.class)
class JdbcClientConfiguration {

	@Bean
	@Primary
	JdbcClient jdbcClient(NamedParameterJdbcTemplate jdbcTemplate) {
		return JdbcClient.create(jdbcTemplate);
	}

}

[philwebb]

Reopening as I think we need a MyBean.kt file for the docs.

[snicoll]

Added in 3835e25