Various UWP GStreamer improvements
There are a number of positive changes in these commits:
* we successfully load GStreamer plugins in ARM64 UWP builds
* we correctly link the ARM64 ANGLE libraries when appropriate
* it is no longer necessary to manually set the LIB environment variable on Windows
* we automatically download and link against UWP-friendly GStreamer binaries when building with `--uwp`
* the use of vcruntime140.dll, msvcp140.dll and api-ms-win-crt-runtime-l1-1-0.dll in the UWP application has been removed and the build does not repackage them
* the set of base supporting GStreamer DLLs has been expanded to allow the gstlibav plugin to load correctly
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- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix#23742
- [x] There are tests for these changes
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Make Windows arm64 easy
* Add a ServoApp project configuration
* Add a `--win-arm64` build flag (now `python mach build -r --win-arm64 --uwp`)
* Automatically set up GStreamer LIB environment
* Yell if the cross-compilation environment isn't set up correctly
* Automatically find the Visual C++ installation for DLL packaging, rather than relying on an environment variable
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- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix#23793 and fix#23795
- [x] There are tests for these changes
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Support WebAudio on Windows
These changes improve the GStreamer experience on Windows in several ways:
* we package the set of plugins and their dependencies that Servo requires for media support
* we explicitly load those plugins when starting the media engine rather than relying on an existing gstreamer installation
These changes do not affect the experience on non-Windows platforms, but the path is clear to do so in order to fix problems like #23519. With these changes I can successfully hear a tone when loading https://joshmatthews.net/osc.html in both a desktop build and a UWP build.
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- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix#23631 and fix#23698
- [x] These changes do not require tests because no tests on windows ;_;
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Filter intermittent wdspec tests failures
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With this change, the intermittent failures for wdspec tests will be filtered and reported.
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- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
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Build simpleservo on Windows
The mozangle change means that we don't rebuild mozangle (and transitively script) because the requested features are different when building libsimpleservo.
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