Add Windows application manifest

[juli27]

The manifest contains five things:

• declare compatibility with Windows 10 & 11
  • we were running inside a Windows Vista compatibility context before (see Details tab in TaskManager, column "Operating system context")
• set process DPI awareness to PerMonitorV2
  • this is already set by Qt programmatically at start up (see Details tab in TaskManager, column "DPI awareness")
• use v6 instead of v5 of the CommonControls library
  • enable modern styles in system dialogs
• user account control settings
  • for completeness. The linker adds that by default anyway, so this was already part of the executable
• set active code page to UTF-8
  • yay

The compatibility declaration with Windows 10 & 11 might change behavior or might not. (I don't expect any changes in behavior)
Another thing we could do is set the process's codepage to UTF-8¹. This might allow as to drop this call to QTextCodec::setCodecForLocale from Qt6Core5Compat.

Print dialog with Windows 10:

Before	After

• I signed the CLA
• The title of the PR describes the problem it addresses
• Each commit's message describes its purpose and effects, and references the issue it resolves
• If changes are extensive, there is a sequence of easily reviewable commits
• The code in the PR follows the coding rules
• There are no unnecessary changes
• The code compiles and runs on my machine, preferably after each commit individually
• I created a unit test or vtest to verify the changes I made (if applicable)

Footnotes

1. https://learn.microsoft.com/en-us/windows/win32/sbscs/application-manifests#activecodepage ↩

[cbjeukendrup]

Another thing we could do is set the process's codepage to UTF-81. This might allow as to drop this call to QTextCodec::setCodecForLocale from Qt6Core5Compat.

That might be nice to try, because depending on Qt5Compat isn't ideal.

[cbjeukendrup]

@DmitryArefiev This one only needs testing on Windows. Just a small regression check; maybe the following things:

• app launches correctly
• no regression in functionality of putting main window full screen and moving it around
• popups work okay (no reason to assume they wouldn't, but let's be sure)
• save/open/print dialogs work fine
• command line mode (just one simple file conversion suffices); with special characters in file names

[DmitryArefiev]

@DmitryArefiev This one only needs testing on Windows. Just a small regression check; maybe the following things:

* app launches correctly

* no regression in functionality of putting main window full screen and moving it around

* popups work okay (no reason to assume they wouldn't, but let's be sure)

* save/open/print dialogs work fine

* command line mode (just one simple file conversion suffices); with special characters in file names

@cbjeukendrup Tested on Win10. PASS. Please review if needed (or just merge)