Add Checkstyle Rule for Objects.notNull

[RussellSpitzer]

We prefer Preconditions.notNull in the project (cc: @findepi ) so we should make it a failing rule in the checkstyle tests. Like we ban usages of new HashMap() here

https://github.com/apache/iceberg/blob/master/.baseline/checkstyle/checkstyle.xml#L54-L57

[tal66]

is this what you mean?:

<module name="RegexpSinglelineJava">
        <property name="format" value="Objects\.requireNonNull.*\(.*\)"/>
        <property name="message" value="Prefer using Preconditions.checkNotNull(Object, String)."/>
</module>

this includes: Objects.requireNonNull() + .requireNonNullElse();

second option:
value="Objects\.(require|)[Nn]onNull.*\(.*\)" - the above + Objects.nonNull().

could add it in line 340.

[RussellSpitzer]

Yep exactly something like although I haven't checked the regexes you put in there :)

[RussellSpitzer]

If you do submit a PR please add a few console logs of the rule in action and failing a build