Previously, the LibWeb bindings generator would output multiple per
interface files like Prototype/Constructor/Namespace/GlobalMixin
depending on the contents of that IDL file.
This complicates the build system as it means that it does not know
what files will be generated without knowledge of the contents of that
IDL file.
Instead, for each IDL file only generate a single Bindings/<IDLFile>.h
and Bindings/<IDLFile>.cpp.
This commit removes the -Wno-unusued-private-field flag, thus
reenabling the warning. Unused field were either removed or marked
[[maybe_unused]] when unsure.
This is to resolve naming conflicts between the ServiceWorker JS exposed
object and the internal representation of a ServiceWorker which is going
to be stored cross process.
