RFR: 8241716: Jpackage functionality to let users choose whether to create shortcuts

[Alexey Semenyuk]

Add support to insert dialog with prompts to create shortcuts in dialog installation sequence of Windows installers created by jpackage.
As a side effect of the fix, UI-related WiX source code was moved from main.wxs into generated ui.wxf file. Users can override ui.wxf by placing a file with this name in resource directory.
Custom dialogs optionally inserted in dialog installation sequence were placed in distinct WiX sources: InstallDirNotEmptyDlg.wxs and ShortcutPromptDlg.wxs. They can be overridden if files with the corresponding names as placed in resource directory.
Moving source code of installer UI from main.wxs into ui.wxf, InstallDirNotEmptyDlg.wxs and ShortcutPromptDlg.wxs files supposed to simplify overriding of the default UI provided by jpackage.

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Commit messages:
 - 8241716: Jpackage functionality to let users choose whether to create shortcuts
 - 8241716: Jpackage functionality to let users choose whether to create shortcuts

Changes: https://git.openjdk.java.net/jdk/pull/2882/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=2882&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8241716
  Stats: 3069 lines in 23 files changed: 2062 ins; 988 del; 19 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2882.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2882/head:pull/2882

PR: https://git.openjdk.java.net/jdk/pull/2882