RFR: 8344451: Deprecate for removal java.awt.Window.getWarningString()

[Phil Race]

This fix deprecates for removal java.awt.Window.getWarningString() and also javax.swing.JInternalFrame.getWarningString()
l java.awt.Window.getWarningString() is only relevant with a SecurityManager and javax.swing.JInternalFrame.getWarningString() is just there for symmetry.

A few other spec changes ensue - the serial form variable warningString is removed is the main one.
The AWTPermission showWindowWithoutWarningBanner is obsolete
Reference to the system property  "awt.appletWarning" was actually already removed by JEP 486

There is a CSR for the spec. changes, which will need a reviewer : https://bugs.openjdk.org/browse/JDK-8344451

But the vast majority of the changes here are all the downstream obsoleted implementation
The warning string and warning icon, and warning windows are all obsoleted.
I think I tracked down all of it, but it is hard to be sure.
Automated tests are passing, and I've manually tested SwingSet2 on all 3 platforms.

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Commit messages:
 - 8344451

Changes: https://git.openjdk.org/jdk/pull/22221/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=22221&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8344451
  Stats: 2028 lines in 39 files changed: 5 ins; 2014 del; 9 mod
  Patch: https://git.openjdk.org/jdk/pull/22221.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22221/head:pull/22221

PR: https://git.openjdk.org/jdk/pull/22221