Windows QPA plugin: Fix debug formatting.

- Introduce QDebugStateSaver for all debug operators.
- Remove the "Flags=" from enumerations since their type is now output
  by default.
- Added some spaces since the previous formatting relied on space=true
  as a result of some debug operators erroneously returning debug.space(),
  which is now fixed in qtbase.
- Fixed formatting, added noquote() where necessary, added some newlines,
  used stream modifiers instead of QString::number(n, 16) to output
  hex numbers.
- Fix indentation.

Change-Id: I64123a4262916e21448cda2aa61ae1100f07291a
Reviewed-by: Joerg Bornemann <joerg.bornemann@theqtcompany.com>