[Java][Spring] Fix #13365 Adjusted pojo.mustache to handle required fields when beanValidation false

[DeaneOC]

When a field was marked as required and beanValidation was false the @NotNull field was missing. The pojo.mustache has been updated to include this. This resolves #13365 and #13196

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[wing328]

@DeaneOC can you please resolve the merge conflicts when you've time?

[DeaneOC]

@wing328 Conflicts resolved.