RFR: 8285693: Create an automated test for JDK-4702199

[Srinivas Mandalika]

reate an automated test for [JDK-4702199](https://bugs.openjdk.java.net/browse/JDK-4702199)

In order for spatial Braille to work and screen reader "review mode", we need bounding rectangle information for all text on the screen, and also the ability to get text substrings. StarOffice 6.1, Netscape and GNOME accessibility also require this new interface for describing text in their applications. This new interface is required for accessibility to StarOffice 6.1, Netscape and GNOME applications as required by Section 508

The solution is to define a new interface and related two helper classes.
AccessibleExtendedText,
AccessibleTextSequence.
AccessibleAttributeSequence

The test validates the public fields of the above classes.
This review is for migrating tests from a closed test suite to open.

Testing:
The test ran successfully on Mach5 with multiple runs (30) on windows-x64, linux-x64 and macos-x64.

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Commit messages:
 - 8285693: Create an automated test for JDK-4702199

Changes: https://git.openjdk.java.net/jdk/pull/8416/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8416&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8285693
  Stats: 96 lines in 1 file changed: 96 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8416.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8416/head:pull/8416

PR: https://git.openjdk.java.net/jdk/pull/8416