This reverts commit 78689d34.

This reverts commit 94ff5202.

This reverts commit 5fd259be.

This fixes VisualDensity.effectiveConstraints to clamp to the max values of the constraint, instead of to double.infinity.

Based on feedback from various desktop developers, and to be consistent between the defaults and the sample code, this PR switches the default for visual density in desktop themes to be compact instead of standard.

It also removes the same setting from the sample code generated by "flutter create" because it is no longer needed now that it is the default.

This reverts commit cb4b8677.

Create a new TextSelectionTheme for text selection properties.

* add language version 2.8 in packages/flutter

* enable non-nullable analyzer flag

Adds a VisualDensity.adaptivePlatformDensity static function that returns different values for visual density based on the defaultTargetPlatform. Returns compact for desktop platforms, and a default visual density for other platforms.