RFR: 8265418: Clean-up redundant null-checks of Class.getPackageName() [v3]

[Сергей Цыпанов]

On Thu, 27 May 2021 11:19:24 GMT, Сергей Цыпанов <github.com+10835776+stsypanov at openjdk.org> wrote:

>> As discussed in https://github.com/openjdk/jdk/pull/3464 we can clean-up null-checks remaining after [8142968](https://bugs.openjdk.java.net/browse/JDK-8142968) as Class.getPackageName() never returns null.
>
> Сергей Цыпанов has updated the pull request incrementally with one additional commit since the last revision:
> 
>   8265418: Compare package names with == instead of equals()

I've looked into history and it appears, that the name of the package has been interned both in `NamedPackage` and `Class` since 8142968 where modular system was introduced

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PR: https://git.openjdk.java.net/jdk/pull/3571