RFR: 8305418: [Linux] Replace obsolete XIM as Input Method Editor [v14]

[Thiago Milczarek Sayao]

> This replaces obsolete XIM and uses gtk api for IME.
> Gtk uses [ibus](https://github.com/ibus/ibus)
> 
> Gtk3+ uses relative positioning (as Wayland does), so I've added a Relative positioning on `InputMethodRequest`.
> 
> [Screencast from 17-09-2023 21:59:04.webm](https://github.com/openjdk/jfx/assets/30704286/6c398e39-55a3-4420-86a2-beff07b549d3)

Thiago Milczarek Sayao has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 88 commits:

 - - Use a work-around to relative positioning (until wayland is not officially supported)
   - Unref pango attr list
 - Merge branch 'master' into new_ime
 - Account the case of !filtered
 - Fix change of focus when on preedit + add filter on key release
 - Merge branch 'master' into new_ime
 - Remove unused include
 - Make it a default method for compatibility
 - Fix JavaDoc
 - Fix @Override
 - Forgot one check
 - ... and 78 more: https://git.openjdk.org/jfx/compare/8872f7af...ba03adce

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Changes: https://git.openjdk.org/jfx/pull/1080/files
 Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1080&range=13
  Stats: 462 lines in 7 files changed: 72 ins; 291 del; 99 mod
  Patch: https://git.openjdk.org/jfx/pull/1080.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1080/head:pull/1080

PR: https://git.openjdk.org/jfx/pull/1080