* GH-2971: Add `LockRegistry.executeLocked()` API
Fixes https://github.com/spring-projects/spring-integration/issues/2971
* Following best practice and well-known patterns with `Jdbc`, `Rest` or `Jms` templates,
introduce `default` methods into `LockRegistry` interface to make it easier to perform
tasks when within a lock.
* Since all the required logic is now covered by those `LockRegistry.executeLocked()` methods,
there is no need in the dedicated abstract `WhileLockedProcessor` class.
Deprecated it for removal in the next version
* Use a new `LockRegistry.executeLocked()` API in the `FileWritingMessageHandler`
instead of just deprecated `WhileLockedProcessor`
* To satisfy Java limitations for checked lambdas, introduce `CheckedCallable` and `CheckedRunnable` utilities
similar to interfaces in the `io.micrometer.observation.Observation`
* Change existing `CheckedFunction` to expose extra generic argument for `Throwable`
* Add dedicated chapter for distributed lock into docs
* Fix some links and typos in the docs
* * Fix Javadoc for `CheckedFunction`
* Fix language in docs
Co-authored-by: Gary Russell <grussell@vmware.com>
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Co-authored-by: Gary Russell <grussell@vmware.com>
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