[API] Fix throwing null exception and add error prone suppression to runSafely functions

[kbendick]

The runSafely function gives an error prone warning for throwing from a finally block.

Originally, we fixed this via suppression in #5190, but I noticed this function was unused and so chose to deprecate it instead in #5205.

@rdblue wanted to keep the function, as it's tested and could be useful in the future.

So this PR:

• fixes the issue discovered in [API] Fix ErrorProne warnings in API module #5190 of throwing failure when it's null
• attempts to throw failure after adding e as a suppressed error when it's non-null
• adds the @Finally suppression to remove the error prone log from the build.

Warning that is logged on build:

iceberg/api/src/main/java/org/apache/iceberg/util/ExceptionUtil.java:124: warning: [Finally] If you return or throw from a finally, then values returned or thrown from the try-catch block will be ignored. Consider using try-with-resources instead.
            throw new RuntimeException("Unknown exception in finally block", failure);
            ^
    (see https://errorprone.info/bugpattern/Finally)

[kbendick]

I moved this log because we're not suppressing e in the other block.

[dimas-b]

This is probably not necessary and actually goes against the ErrorProne guideline of not throwing from finally.

The only way failure can be non-null here is if it was thrown from the main try block, in which case the generated bytecode will ensure it is re-thrown when finally completes.

[rdblue]

In this case, failure is already thrown because it is thrown in the catch block. tryThrowAs needs to be removed here. The logic was correct before, except for the wrong exception in the next block.

[kbendick]

TIL. Will remove. Thanks guys.

[kbendick]

Oh actually yeah I understand. The failure would have already been thrown, just the finally block gets run and we add one more suppression to it. So we don't need to throw it again. Thanks for the explanation.

[rdblue]

Thanks, @kbendick!