84153 Migrate dartdoc to null safety (team, cla: yes, waiting for tree to go green, a: null-safety, tech-debt)

84156 Re-land “Migrate android_semantics_testing to null safety (#84136)” (team, a: accessibility, cla: yes, waiting for tree to go green, a: null-safety, tech-debt)

84227 Migrate android application_package to null safety (team, tool, cla: yes, waiting for tree to go green, a: null-safety)

84372 Fix assemble iOS codesign flag to support –no-sound-null-safety (platform-ios, tool, cla: yes, waiting for tree to go green, t: xcode, a: null-safety)