Introduce `Builder` API and factory methods for `RetryPolicy`

[sbrannen]

Overview

We currently have three concrete implementations of RetryPolicy.

• MaxRetryAttemptsPolicy
• MaxDurationAttemptsPolicy
• PredicateRetryPolicy

Users may wish to combine certain features, such as max attempts plus a custom predicate.

However, there is no way to combine the behavior of those policies.

Furthermore, the PredicateRetryPolicy is practically useless as a standalone policy: it does not have a way to end an infinite loop if the Retryable continually throws an exception that matches the predicate.

In light of the above, we should replace the current built-in RetryPolicy implementations with a fluent Builder API and dedicated factory methods for common use cases.

In addition, we know that we will need to support "include" and "exclude" lists of exception types which a policy should honor. For example, the @Retryable annotation will likely allow users to specify those lists declaratively.

Thus, we should also provide built-in support for specifying include/exclude lists.

Related Issues

• Revise RetryTemplate for alignment with Reactor (in preparation for @Retryable) #35057
• Introduce @Retryable AOP support (based on core.retry and Reactor retry functionality) #34529

Example Usage

new MaxRetryAttemptsPolicy(5)

Gets replaced with:

RetryPolicy.withMaxAttempts(5)

---

new MaxDurationAttemptsPolicy(Duration.ofSeconds(5))

Gets replaced with:

RetryPolicy.withMaxDuration(Duration.ofSeconds(5))

---

new PredicateRetryPolicy(IOException.class::isInstance)

Gets replaced with:

RetryPolicy.builder()
    .maxAttempts(3)
    .predicate(IOException.class::isInstance)
    .build();

---

The following example demonstrates all supported features of the builder.

var retryPolicy = RetryPolicy.builder()
        .maxAttempts(5)
        .maxDuration(Duration.ofMillis(100))
        .includes(IOException.class)
        .excludes(FileNotFoundException.class)
        .predicate(t -> t.getMessage().contains("Unexpected failure"))
        .build();