PageSetupDialog incorrectly converts Margin units from pageSetting.Margins to dialogSettings.rtMargin

### .NET version 10.0.201 ### Did it work in .NET Framework? Yes ### Did it work in any of the earlier releases of .NET Core or .NET 5+? Did not test. ### Issue description Method `PageSetupDialog.RunDialog(IntPtr hwndOwner)` incorrectly detects `toUnit` based on Windows regional settings. In Windows for my user account, `Language & region > Number settings, Measurement System` is set to `Metric`. When I open `PageSetupDialog` from my .Net application, it displays Margins group with caption "Margins (millimeters)". Every time I open this dialog, don't change anything, and close it - margin values are reduced until they become 0. After analyzing PageSetupDialog.cs and PrinterUnitConvert.cs, checking values of `PrintDocument.DefaultPageSettings.Margins` and what is shown in the dialog fields, and doing manual calculations, I see that: 1. In method `RunDialog` original values from `pageSettings.Margins` converted using `toUnit` == `PrinterUnit.ThousandthsOfAnInch`. 2. In method `UpdateSettings` new values converted to `pageSettings.Margins` using `fromUnit` == `PrinterUnit.HundredthsOfAMillimeter`. Comparing with source code for .Net Framework 4.8, I see that there is difference in getting locale info: - .Net Framework 4.8 checks `NativeMethods.LOCALE_USER_DEFAULT` - user level; - .Net 10 checks `PInvoke.LOCALE_NAME_SYSTEM_DEFAULT` - system level; I suspect the issues is here - logic of PageSetupDialog checks system level locale settings, but dialog itself when run by Windows uses user level locale settings (and sets flag PSD_INHUNDREDTHSOFMILLIMETERS to not 0), so it results in display discrepancy and different conversion units used with original and new values. ### Steps to reproduce Set `Language & region > Number settings, Measurement System` on system level to `U.S.`, and on user level to `Metric`.