Link rendering: Add support for UrlMode parameter in HtmlLocalLinkParser (port to 16)

[AndyButland]

Forward port of #20200 that required a bit more than just a cherry-pick.

In doing so I noticed we had a method that takes a preview parameter that was never used, as the method just delegated to the overload without that parameter. So I've obsoleted that and amended each of the callers.

Unit tests should verify the changes but a manual test can also be done in a view with e.g:

@inject HtmlLocalLinkParser LocalLinkParser;
<div>@LocalLinkParser.EnsureInternalLinks("a href=\"{localLink:4148}\"")</div>
<div>@LocalLinkParser.EnsureInternalLinks("a href=\"{localLink:4148}\"", UrlMode.Absolute)</div>

You should see the URL created with the expected URL mode.

[Copilot]

Pull Request Overview

This PR adds support for a UrlMode parameter to the HtmlLocalLinkParser class, allowing developers to specify how URLs should be rendered (relative, absolute, etc.) when parsing local links. The change is being ported to version 16.

Key changes:

• Added new overload to EnsureInternalLinks method accepting UrlMode parameter
• Updated internal URL generation to respect the specified UrlMode
• Marked the preview-based overload as obsolete

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/Umbraco.Core/Templates/HtmlLocalLinkParser.cs	Added new EnsureInternalLinks overload with UrlMode parameter and updated URL generation logic
src/Umbraco.Core/PropertyEditors/TextStringValueConverter.cs	Removed preview parameter from EnsureInternalLinks call
src/Umbraco.Infrastructure/PropertyEditors/ValueConverters/MarkdownEditorValueConverter.cs	Removed preview parameter from EnsureInternalLinks call
src/Umbraco.Infrastructure/PropertyEditors/ValueConverters/RteBlockRenderingValueConverter.cs	Removed preview parameter from EnsureInternalLinks call
tests/Umbraco.Tests.UnitTests/Umbraco.Core/Templates/HtmlLocalLinkParserTests.cs	Added comprehensive unit tests for the new UrlMode functionality

[kjac]

Great work, @AndyButland 💪