RFR: JDK-8340077 : Open source few Checkbox tests - Set2

[Harshitha Onkar]

Following tests are updated in this PR:

1. 	test/jdk/java/awt/Checkbox/CheckboxBoxSizeTest.java
2. 	test/jdk/java/awt/Checkbox/CheckboxIndicatorSizeTest.java
3. 	test/jdk/java/awt/Checkbox/CheckboxNullLabelTest.java
4. 	test/jdk/java/awt/Checkbox/CheckboxPreferredSizeTest.java

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Commit messages:
 - eof newline
 - checkbox tests

Changes: https://git.openjdk.org/jdk/pull/21094/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21094&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8340077
  Stats: 409 lines in 4 files changed: 409 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/21094.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21094/head:pull/21094

PR: https://git.openjdk.org/jdk/pull/21094