[4.x] Treeselect fixes

[C-Lodder]

Pull Request for Issue #41309

Summary of Changes

1. Fix the treeselect dropdowns not working
2. Fix the check/uncheck buttons not toggling checkboxes that had been manually changed (backported from [5.1] Rewrite treeselect in vanilla JS #42776)
3. Fix select/deselect changing the state of the current menu (backported from [5.1] Rewrite treeselect in vanilla JS #42776)

Testing Instructions

1. Go to edit any module in the Module Manager
2. Navigate to the Menu Assignment tab
3. Change the assignment to "Only on selected pages"

Test 1:
Ensure the dropdown menu opens as shown below:

Test 2:

1. Open the dropdown menu and click "select" or "unselect"
   All checkboxes (including the one parallel to the dropdown toggle) should be toggled

Test 3:

1. Check (or uncheck) any checkbox
2. Click the buttons shown above:
   

All checkboxes should be toggled.

@LadySolveig @Quy

[Quy]

Can this be improved to not toggle disabled checkboxes?

[C-Lodder]

@Quy - It wouldn't make the UX better to be honest. If a checkbox appears to be "disabled" (as shown in your screenshot), I'd assume I wouldn't be able to manually check it, which the user should be able to.

[Quy]

It is unchecked and not toggleble by default for URL, Alias, Heading, however, the All/None and Select/Deselect toggle them. Ideally, they should be skipped with these actions.

[C-Lodder]

Oh I see. Didn't know that was the expected behavior. Will take a look tomorrow morning

[C-Lodder]

@Quy fixed

[ghost]

I have tested this item ✅ successfully on 1ce3ae6

Test by using prebuilt package:

PR having label NPM Resource Changed can't be tested by Patchtester.

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[Quy]

I have tested this item ✅ successfully on 1ce3ae6

Thank you!!!

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[Quy]

RTC

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[laoneo]

@C-Lodder can you fix the whitespaces?

[C-Lodder]

@laoneo Done.
Silly windows eol

[laoneo]

@C-Lodder thanks

[laoneo]

Thanks!