Migrate spring-retry RetryTemplate configuration to Spring Framework 7 RetryPolicy.builder()

Rewrite spring-retry RetryTemplate construction to Spring Framework 7's new RetryTemplate(RetryPolicy.builder()...build()): RetryTemplate.builder() chains, including a customPolicy constructed inline or in a local used only there, RetryTemplate.defaultInstance(), and new RetryTemplate() configured in the same method through setRetryPolicy / setBackOffPolicy with SimpleRetryPolicy, MaxAttemptsRetryPolicy, NeverRetryPolicy, AlwaysRetryPolicy, TimeoutRetryPolicy, NoBackOffPolicy, FixedBackOffPolicy or ExponentialBackOffPolicy, including classifier maps built from literals. spring-retry's defaults are made explicit since Spring Framework 7's differ. Configuration with no exact Spring Framework 7 equivalent is left unchanged.