Add unit tests for UI layouts package (#4095)

* Add comprehensive unit tests for layouts package

Created extensive unit tests for the following layout classes:
- BorderLayoutTest: Tests for all constraints (NORTH, SOUTH, EAST, WEST,
  CENTER, OVERLAY), center behaviors, landscape swap, scale edges, and
  factory methods
- BoxLayoutTest: Tests for X_AXIS, Y_AXIS, X_AXIS_NO_GROW, Y_AXIS_BOTTOM_LAST,
  alignment options, and all factory methods
- FlowLayoutTest: Tests for horizontal/vertical alignment, fill rows,
  valign by row, and all enclose factory methods
- GridLayoutTest: Tests for row/column configuration, auto-fit, fill last row,
  hide zero sized, and landscape mode
- LayeredLayoutTest: Tests for component layering, preferred size in MM,
  and overlap behavior
- CoordinateLayoutTest: Tests for absolute positioning, scaling, and
  coordinate transformation

All tests follow existing conventions:
- Extend UITestBase for Display initialization
- Use JUnit 5 annotations and assertions
- Avoid Mockito (use TestCodenameOneImplementation instead)
- Test both API and layout behavior
- Aim for high code coverage

Tests cover constructors, getters/setters, factory methods, layout
calculations, preferred size calculations, edge cases, and equals/toString
methods for each layout class.

* Fix layout tests: Use @formtest and Dimension for setSize

- Changed setSize(int, int) to setSize(new Dimension(int, int))
- Changed @test to @formtest for tests that call layoutContainer()
- Added FormTest import to all test files
- Tests that only test API methods remain as @test
- Layout tests that need Form context now use @formtest

* Fix BorderLayoutTest failures

- Changed exact position check to allow for container padding
- Fixed component reuse across multiple containers in factory tests
- Each factory method now tests with a separate label instance

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Co-authored-by: Claude <[email protected]>

Author: shai-almog