[WASM] Qt's internal shaders can easily conflict with user shaders

Steps to reproduce

1. Load the Shader Effects example (https://doc.qt.io/qt-6/qtquick-shadereffects-example.html )
2. Edit shadereffects.qml to add one line, "import QtMultimedia"
3. Re-run CMake
4. Build the project

Note: After step #2, it is necessary to re-run CMake (or delete the build folder entirely) if the project was previously built. Simply cleaning the project is not enough.

Outcomes
The build fails with the following error:

wasm-ld: error: duplicate symbol: qInitResources_shaders()
>>> defined in CMakeFiles/shadereffectsexample.dir/.rcc/qrc_shaders.cpp.o
>>> defined in C:/Qt/6.5.3/wasm_multithread/lib/objects-Release/Multimedia_resources_1/.rcc/qrc_shaders.cpp.o

wasm-ld: error: duplicate symbol: qCleanupResources_shaders()
>>> defined in CMakeFiles/shadereffectsexample.dir/.rcc/qrc_shaders.cpp.o
>>> defined in C:/Qt/6.5.3/wasm_multithread/lib/objects-Release/Multimedia_resources_1/.rcc/qrc_shaders.cpp.o

Workaround/Fix

• Users: Pass a name that's not "shaders" to qt6_add_shaders()
• Qt: Pass a name that's not "shaders" to qt_internal_add_shaders() (see https://github.com/qt/qtmultimedia/blob/v6.5.3/src/multimedia/CMakeLists.txt#L285 for example)