RFR: JDK-8248264: WinUpgradeUUIDTest application is missing in downgrade scenario

[Alexey Semenyuk]

Please review fix [2] for jpackage bug [1].

Put `RemoveExistingProducts` action before `CostInitialize` action in 
`InstallExecuteSequence` sequence to uninstall existing product(s) 
before installer makes changes to the file system.
Existing Wix `MajorUpgrade` elements in main.wxs implicitely add 
`RemoveExistingProducts` action to `InstallExecuteSequence` sequence but 
not in the required order. Thus all `MajorUpgrade` elements in main.wxs 
were replaced with explicitly defined upgrade table.

- Alexey

[1] https://bugs.openjdk.java.net/browse/JDK-8248264

[2] http://cr.openjdk.java.net/~asemenyuk/8248264/webrev.00