feat(api): add exchange property and variable helpers

[squakez]

Closes CAMEL-22910

This one could be a good helper for final users to spare time on casting and using raw types. The new utility methods allow the user passing from the following:

        @SuppressWarnings("unchecked")
        List<String> values =
            myExchange.getProperty("myProp", List.class);

to:

        List<String> values = myExchange.getPropertyAsList("myProp", String.class);

There are also utilities for Map, Collections, Set and Optional on getProperty and getVariable.

Description

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• I checked that each commit in the pull request has a meaningful subject line and body.

• I have run mvn clean install -DskipTests locally from root folder and I have committed all auto-generated changes.

[squakez]

Should we return null, skip the item or throw the exception? I had followed the original API, for which any error on the cast of the property would return null. But maybe we can change it in these implementations.

[Croway]

what about skipping and LOG.warn the skipped element?

[squakez]

Same question about the casting posed above.

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[davsclaus]

Beware the Exchange API is already big and its a central API for Camel end users.

End users should use variables and not exchange properties. The latter is more for Camel internally and component developers and old school before variables was added to Camel.

We have ExchangeHelper where extra methods is better suited that are not commonly in use, or would rarely need to be.

So if you have some internal API cleanup where you want to remove those suppress warning then IMHO its not new methods on Exchange we should add, but on ExchangeHelper and then use that internally in Camel.

[orpiske]

Please note that this isIstance check within a loop is very likely to hit the JVM secondary super issue which triggers a false sharing problem and affects pretty much everything older than Java 22.

[squakez]

Thanks for the reviews, the goal of this PR is more kind of experimental to provide some simplification to both final users and internal development as well. More than just skipping the warnings it is an attempt to bring some easier API for the final user. I will move them into the ExchangeHelper. I was also thinking to do some similar upper layer API for making it simpler to extract the body. I'll keep it as a draft while I continue refining these possibilities.