RFR: Fix deprecation warnings coming from JDK 16 [v2]

[Sergei Ustimenko]

> This PR fixes compilation warnings that fail builds during compilation because of -Werror flag.
> The issues with compilation appear on JDK 16. Warnings that were fixed:
> - warning: [missing-explicit-ctor] class JTRegModuleHelper in exported package java.lang declares no explicit constructors, thereby exposing a default constructor to clients of module java.base
> - SimpleReporter.java:*: warning: [removal] Integer(int) in Integer has been deprecated and marked for removal 
> 
> After the changes build passes.

Sergei Ustimenko has updated the pull request incrementally with one additional commit since the last revision:

  Update copyrights

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Changes:
  - all: https://git.openjdk.java.net/jtreg/pull/15/files
  - new: https://git.openjdk.java.net/jtreg/pull/15/files/88d8ca44..9653b2bb

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jtreg&pr=15&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jtreg&pr=15&range=00-01

  Stats: 2 lines in 2 files changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jtreg/pull/15.diff
  Fetch: git fetch https://git.openjdk.java.net/jtreg pull/15/head:pull/15

PR: https://git.openjdk.java.net/jtreg/pull/15