RFR: 8290844: Add Skin.install() method [v15]

[Kevin Rushforth]

On Fri, 28 Oct 2022 07:58:40 GMT, John Hendrikx <jhendrikx at openjdk.org> wrote:

>> (and it was me who added @Test(expected=IllegalArgumentException.class) test)
>
> I said it wrong, the asserts can be used in both 4 and 5, so `assertThrows` can always be used now that it is available (the upgrade to JUnit 5 also updated JUnit 4 to a version which supports `assertThrows`).

In that case, this is fine. What I meant when I said we don't want to mix 4 and 5 in the same file is that we should not use some APIs from JUnit 4 (e.g., `org.junit.Assert`) and some from JUnit 5 (e.g., `org.junit.jupiter.api.Assertions`) in the same file.

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PR: https://git.openjdk.org/jfx/pull/845