fix(#831): Fixed pristine attribute reflection to be in spec

[Ellarddekoeijer]

The way the pristine attribute is currently reflected is incorrect and not in-line with the spec for web components. The UI Library currently only works with Lit because of this.

#831 describes this in further detail.

Description

I opted to remove the getters and setters. Check on connectedCallback instead of the constructor, as this caused the issue in the first place. The code mostly documents itself, due to its small nature :)

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Chore (minor updates related to the tooling or maintenance of the repository, does not impact compiled assets)

Motivation and context

It solves issue #831

How to test?

Interact with an input element, verify that the pristine attribute still works properly

Checklist

• If my change requires a change to the documentation, I have updated the documentation in this pull request.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes. (not needed..?)

[github-actions]

Hi there @Ellarddekoeijer, thank you for this contribution! 👍

While we wait for the team to have a look at your work, we wanted to let you know about that we have a checklist for some of the things we will consider during review:

• It's clear what problem this is solving, there's a connected issue or a description of what the changes do and how to test them
• The automated tests all pass (see "Checks" tab on this PR)
• The level of security for this contribution is the same or improved
• The level of performance for this contribution is the same or improved
• Avoids creating breaking changes; note that behavioral changes might also be perceived as breaking
• If this is a new feature, Umbraco HQ provided guidance on the implementation beforehand
• 💡 The contribution looks original and the contributor is presumably allowed to share it

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud