Optimize View drawing logic and update ClearViewport tests

Refactored the `View` class to include a `NeedsDraw` check in
multiple drawing methods, improving rendering efficiency.
Adjusted `OnDrewText` and `DrewText` event handling for
consistency. Removed unused code and redundant tests.

Rewrote and reorganized `ClearViewportTests` for clarity and
compatibility with the new `NeedsDraw` logic. Added new tests
to validate `ClearViewport` behavior under various conditions,
including transparent viewports, event cancellations, and
content-only clearing.

Updated namespaces for better alignment, disabled a noisy
`ComboBoxTests` test, and improved code formatting and
maintainability across files.

Tests/UnitTestsParallelizable/Drawing/Lines/StraightLineExtensionsTests.cs

@@ -1,7 +1,7 @@
 using UnitTests;
 using Xunit.Abstractions;
 
-namespace UnitTests.Parallelizable.Drawing.Lines;
+namespace DrawingTests.Lines;
 
 public class StraightLineExtensionsTests (ITestOutputHelper output)
 {