RFR: JDK-8315951: Open source several Swing HTMLEditorKit related tests

[Harshitha Onkar]

Following tests are open sourced as part of this PR.

1. java/awt/event/PaintEvent/RepaintTest/RepaintTest.java
2. javax/swing/text/html/HTMLEditorKit/4214848/bug4214848.java
3. javax/swing/text/html/HTMLEditorKit/4230197/bug4230197.java
4. javax/swing/text/html/HTMLEditorKit/4238223/bug4238223.java

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Commit messages:
 - summary tag updated
 - HTMLEditorKit test changes

Changes: https://git.openjdk.org/jdk/pull/15751/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15751&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8315951
  Stats: 367 lines in 4 files changed: 367 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/15751.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15751/head:pull/15751

PR: https://git.openjdk.org/jdk/pull/15751