RFR: 8344896: Remove obsolete checks for AWTPermission accessClipboard [v2]

[Phil Race]

> This removes the SecurityManager related checks for clipboard access  and methods which exist solely to support that.
> 
> One interesting thing is that there are two places where a method "canAccessSystemClipboard()"  was not only about the SM. 
> In SwingUtilities and InputEvent it would return false in headless mode, regardless of whether there is an SM.
> This means I have left the methods in place, behaving the same as before in headless mode.
> We may be able to further simplify this later  but it will be clearer with the SM-only logic removed and out of scope for this fix.

Phil Race has updated the pull request incrementally with one additional commit since the last revision:

  8344896

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Changes:
  - all: https://git.openjdk.org/jdk/pull/22356/files
  - new: https://git.openjdk.org/jdk/pull/22356/files/23a72b82..efe784a9

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=22356&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=22356&range=00-01

  Stats: 4 lines in 3 files changed: 0 ins; 4 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/22356.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22356/head:pull/22356

PR: https://git.openjdk.org/jdk/pull/22356