RFR: JDK-8307807 Replace use of System.getProperty("os.name") with PlatformUtil calls [v6]

[Lukasz Kostyra]

On Thu, 11 May 2023 20:19:38 GMT, Carl Döbbelin <duke at openjdk.org> wrote:

>> Replaced querying of `System.getProperty("os.name")` to check for OS with the use of the methods provided by `PlatformUtils`
>
> Carl Döbbelin has updated the pull request incrementally with one additional commit since the last revision:
> 
>   made launcherimpl one line

Looks good, tests are passing as expected on all platforms

-------------

Marked as reviewed by lkostyra (Author).

PR Review: https://git.openjdk.org/jfx/pull/1132#pullrequestreview-1424313030