RFR: 8352793: Open source several AWT TextComponent tests - Batch 1

[Tejesh R]

Open source these AWT TextComponent tests:

java/awt/TextComponent/BackgroundTest/BackgroundTest.java
java/awt/TextComponent/DisableTest/DisableTest.java
java/awt/TextComponent/TextFieldMargin/TextFieldMargin.java
java/awt/TextComponent/ModifiersTest/ModifiersTest.java

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Commit messages:
 - Open source

Changes: https://git.openjdk.org/jdk/pull/24656/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=24656&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8352793
  Stats: 380 lines in 4 files changed: 380 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/24656.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24656/head:pull/24656

PR: https://git.openjdk.org/jdk/pull/24656