Calendar and DateEntry are not fully localised

[andydotxyz]

Checklist

• I have searched the issue tracker for open issues that relate to the same problem, before opening a new one.
• This issue only relates to a single bug. I will open new issues for any other problems.

Describe the bug

The first day of the week and the date format are static instead of matching the user's locale.

How to reproduce

Use Calendar widget and switch to a locale that has Sunday first instead of Monday.

Use DateEntry and notice that the date format is the same as you switch from English to US English.

Screenshots

No response

Example code

n/a

Fyne version

future pre-2.6 (not a landed feature yet)

Go compiler version

all

Operating system and version

all

Additional Information

No response