RFR: 8324681: Replace NULL with nullptr in HotSpot jtreg test native code files [v5]

[Coleen Phillimore]

> This mechanically replaces NULL with nullptr in hpp/cpp native files in test native code.  This didn't attempt to change NULL in comments to say null because nullptr is generally the right thing for the comment to say.  It does attempt to change NULL to "null" rather than "nullptr" in strings.  Any changes for "nullptr" to "null" in comments can be changed in a future RFE in a smaller patch. I didn't see any when it was scrolling by to make my script more complicated.
> 
> Ran tier1-4 testing.

Coleen Phillimore has updated the pull request incrementally with two additional commits since the last revision:

 - Fix some casts unnecessary with nullptr
 - Fix copyrights

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Changes:
  - all: https://git.openjdk.org/jdk/pull/17593/files
  - new: https://git.openjdk.org/jdk/pull/17593/files/6eb051ed..6ac8aa85

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=17593&range=04
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=17593&range=03-04

  Stats: 32 lines in 27 files changed: 0 ins; 0 del; 32 mod
  Patch: https://git.openjdk.org/jdk/pull/17593.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17593/head:pull/17593

PR: https://git.openjdk.org/jdk/pull/17593