84840 fix _owner nullability in routers.dart (framework, cla: yes, f: routes, will affect goldens, a: null-safety)

84847 Fix documentation of equality functions. (framework, cla: yes, d: api docs, documentation)

84872 Reland: Add optional param to useRootNavigator when showSearch (framework, f: material design, cla: yes, waiting for tree to go green)

84887 Substitute a replacement character for invalid UTF-16 text in a TextSpan (framework, cla: yes, a: typography, waiting for tree to go green)

84988 Adds mainAxisMargin property to RawScrollbar (severe: new feature, framework, f: scrolling, cla: yes, waiting for tree to go green)