Form: implement relayouting instead of full rerender on dimension change

[pharret31]

No description provided.

[Copilot]

Pull request overview

This pull request implements a performance optimization for the DevExtreme Form widget by replacing full rerenders with lightweight relayouting when dimension changes occur (e.g., responsive screen factor changes). Instead of destroying and recreating all widgets, the form now updates only the ResponsiveBox layout and CSS classes, preserving editor instances and their state.

Changes:

• Introduced a relayouting code path that bypasses full rerender when dimension changes trigger a refresh
• Refactored group column count CSS class management into reusable methods for both initial render and updates
• Added helper methods in LayoutManager for updating ResponsiveBox layout and managing CSS classes without full rerender

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
packages/devextreme/js/__internal/ui/form/form.ts	Added _isDimensionChangeRefresh flag, _updateLayoutsOnDimensionChange(), _applyGroupColCount(), and _updateGroupsColCount() methods to support relayouting. Modified _refresh() to use relayouting path for dimension changes. Refactored group column count class application into reusable method.
packages/devextreme/js/__internal/ui/form/form.layout_manager.ts	Added updateResponsiveBoxLayout() method to update ResponsiveBox without full rerender. Added helper methods _getLocationBoundaryFlags(), _getLocationCssClasses(), _getLayoutManagerItemByLocation(), and _updateItemsCssClasses() for CSS class management. Improved type safety by changing _cashedColCount type and removing ts-expect-error comments. Introduced Location and LocationBoundaryFlags type definitions.
packages/devextreme/testing/tests/DevExpress.ui.widgets.form/form.tests.js	Updated test expectations to verify that editors are preserved (not reinitialized) during dimension changes, confirming the relayouting optimization works correctly.