[runtime][java] Add durable reconcile support with reconcile callables

[joeyutong]

Purpose of change

This PR adds Java-side durable reconcile support based on a reconcile callable.

With this change, a DurableCallable can optionally provide a reconcile callable through reconcile(). When recovery hits a PENDING durable call, the runtime invokes that reconcile callable to recover a terminal result or terminal failure, or falls back to executing the original call() when the reconcile path cannot determine the terminal state.

This PR includes:

• a new DurableCallable.reconcile() API for Java durable calls
• a new ReconcileFallbackException to signal fallback to the original call()
• runtime changes in RunnerContextImpl and JavaRunnerContextImpl to route sync and async durable execution through the reconcile path when a reconcile callable is provided
• state model updates in ActionState and CallResult to support PENDING / terminal transitions for reconcile-based recovery
• unit and operator recovery tests covering recovered success, recovered terminal failure, and fallback execution

The detailed design discussion is available here:
design discussion

Tests

This change is covered by:

• ReconcileFallbackExceptionTest
• CallResultTest
• ActionStateTest
• ActionStateSerdeTest
• DurableExecutionContextTest
• RunnerContextImplDurableExecuteTest
• JavaRunnerContextImplDurableExecuteAsyncTest
• ActionExecutionOperatorTest

API

Yes.

This PR introduces Java public API changes:

• DurableCallable adds an optional @Nullable Callable<T> reconcile() hook
• ReconcileFallbackException is added for reconcile fallback signaling
• RunnerContext JavaDoc is updated to describe reconcile-callable durable execution semantics

Documentation

• doc-needed
• doc-not-needed
• doc-included