This commit adds all the missing includes when the PCH header is not used.
Also, some includes are reordered and/or made consistent (e.g. "#include <QtEndian>" -> "#include <QtCore/QtEndian>").
According to Qt's documentation the PCH header doesn't need to be included.
From https://doc.qt.io/qt-5/qmake-precompiledheaders.html:
"To make your project use precompiled headers, you only need to define the PRECOMPILED_HEADER variable in your project file."
"qmake will handle the rest, to ensure the creation and use of the precompiled header file. You do not need to include the precompiled header file in HEADERS, as qmake will do this if the configuration supports precompiled headers."
