RFR: 8265418: Clean-up redundant null-checks of Class.getPackageName() [v2]

[Сергей Цыпанов]

> 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 with a new target base due to a merge or a rebase. The pull request now contains two commits:

 - Merge branch 'master' into 8265418
   
   # Conflicts:
   #	src/java.base/share/classes/java/lang/Class.java
 - 8265418: Clean-up redundant null-checks of Class.getPackageName()

-------------

Changes: https://git.openjdk.java.net/jdk/pull/3571/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3571&range=01
  Stats: 18 lines in 7 files changed: 1 ins; 7 del; 10 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3571.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3571/head:pull/3571

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