RFR: 8286872: Refactor add/modify notification icon (TrayIcon) [v2]

[Alexey Ivanov]

> Encapsulate the logic of adding or modifying a notification icon aka tray icon. This is to avoid code duplication between [`AwtTrayIcon::WmTaskbarCreated`](https://github.com/openjdk/jdk/blob/7b988b31c661c6e3e58cf8ced81732e40a79d4f5/src/java.desktop/windows/native/libawt/windows/awt_TrayIcon.cpp#L477) and [`AwtTrayIcon::_UpdateIcon`](https://github.com/openjdk/jdk/blob/7b988b31c661c6e3e58cf8ced81732e40a79d4f5/src/java.desktop/windows/native/libawt/windows/awt_TrayIcon.cpp#L796).
> 
> Separating adding and modifying the icon simplifies the methods, the actions are clearer: adding the icon requires sending `NIM_SETVERSION` message whereas modifying the icon doesn't.
> 
> To verify the code works as before, I used `TrayIconScalingTest.java`. I killed explorer.exe process to verify the notification icon gets added. Changing DPI of the main display updates the displayed icon as expected.

Alexey Ivanov has updated the pull request incrementally with one additional commit since the last revision:

  8286872: Replace SendTrayMessage(NIM_MODIFY) with ModifyTrayIcon()

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/8749/files
  - new: https://git.openjdk.java.net/jdk/pull/8749/files/2e85731c..67625852

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=8749&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=8749&range=00-01

  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8749.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8749/head:pull/8749

PR: https://git.openjdk.java.net/jdk/pull/8749