[4.0] Subform fixes

[Denitz]

Summary of Changes

Changes in repeatable-table subform layout:

1. Use correct .table-responsive wrapper.
2. Use a unique ID for the subform table.
3. Don't display the field description because it's already displayed as a tooltip in the column header.
4. Remove the implicit style of width:45% for th.

Common changes:

1. Don't pass $subForm param by reference in SubformField::loadSubFormData(Form $subForm) because it's an object.
2. Fix phpdoc in SubformField::setup() for undefined class SimpleXMLElement
3. Propagate originating field ID into subform layouts via $fieldId
4. Make SubformField::loadSubFormData protected for possible override.
5. Fixed actually displayed .control-label.sr-only which still consumed 240px width and broke the table-responsive behavior with screen horizontal scrolling remained.

Testing Instructions

Show multiple subform fields on the same page, use wide forms to require responsive scroller.

Actual result BEFORE applying this Pull Request

Duplicate table IDs, field descriptions below each field, the table is not responsive.

Expected result AFTER applying this Pull Request

Unique table IDs, field descriptions are hidden, the table is responsive.

Documentation Changes Required

No.

[Denitz]

@Quy no conflicts now

[Quy]

Please fix conflicts.

[RickR2H]

I have tested this item ✅ successfully on 2affe23

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_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/31567.}

[Quy]

I have tested this item ✅ successfully on 2affe23

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_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/31567.}

[Quy]

RTC

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_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/31567.}

[richard67]

Thanks!