RFR: 8242505: Some WebKit tests might fail because Microsoft libraries are not loaded

[Kevin Rushforth]

This PR will allow javafx.web unit tests to run to completion and pass on Windows with Visual Studio 2019.

Two of the WebKit tests load the native WebKit library without initializing the JavaFX runtime. This will lead to test
failures and will hang the test run if those tests are run before the other tests, and if the system doesn't have all
the needed runtime libraries.

The simple fix is to call the Toolkit method to load those libraries. This is only needed for unit tests that don't
already initialize the JavaFX runtime (e.g., by calling `Platform::startup` or `Application::launch`) and call internal
methods that execute native code as part of the test.

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Commit messages:
 - 8242505: Some WebKit tests might fail because Microsoft libraries are not loaded

Changes: https://git.openjdk.java.net/jfx/pull/194/files
 Webrev: https://webrevs.openjdk.java.net/jfx/194/webrev.00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8242505
  Stats: 12 lines in 2 files changed: 12 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jfx/pull/194.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/194/head:pull/194

PR: https://git.openjdk.java.net/jfx/pull/194