Allow validation errors on entries without interaction

[kruitbosdotdev]

Description:

Implements a way to show errors without user interaction as described in the issue mentioned below. The main goal was to implement this change without modifying existing tests, ensuring that current behavior remains intact. The default functionality continues to work as expected without setting AlwaysShowValidationError.

All the tests create their testbed from the ground up instead of expanding a single test and doing SetText() for example. This way the tests test the behaviour when the entry is rendered instead of relying on user interaction to tigger a Refresh().

Fixes #5590

Checklist:

• Tests included.
• Lint and formatter run with no errors.
• Tests all pass.

Where applicable:

• Public APIs match existing style and have Since: line.

[andydotxyz]

Thanks for this, unfortunately it came in after the feature freeze and we are now in full release mode.
This should be good to go after that, but will need a "Since: 2.7" line instead.

[kruitbosdotdev]

Will do. I'll also take a look at the failing tests

[coveralls]

coverage: 62.241% (-0.06%) from 62.299%
when pulling c89a5a1 on kruitbosdotdev:implementation-5590
into b252798 on fyne-io:develop.

[andydotxyz]

Thanks for getting this worked out - let's land it and get 2.7 work started :)