RFR: 8150564: Migrate useful ExtendedRobot methods into awt.Robot [v6]

[Alisen Chung]

> Some useful methods in ExtendedRobot should be migrated into Robot itself so that ExtendedRobot can be removed in the future. The tests using ExtendedRobot for these migrated methods are changed to use only Robot (removing unnecessary building of ExtendedRobot).

Alisen Chung has updated the pull request incrementally with one additional commit since the last revision:

  add specification to public default fields

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Changes:
  - all: https://git.openjdk.org/jdk/pull/22044/files
  - new: https://git.openjdk.org/jdk/pull/22044/files/adb0f58f..d330af39

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=22044&range=05
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=22044&range=04-05

  Stats: 9 lines in 1 file changed: 7 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/22044.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22044/head:pull/22044

PR: https://git.openjdk.org/jdk/pull/22044