88914 Fix web_tool_tests failure on dart roll (tool, cla: yes)

88920 Migrate fuchsia sdk and dependencies to null safety (tool, cla: yes, waiting for tree to go green, a: null-safety)

88923 Changed tool cached properties to late finals (tool, cla: yes, waiting for tree to go green, a: null-safety)

88934 Clean up null assumptions in devfs to prep for null safety migration (tool, cla: yes, waiting for tree to go green, a: null-safety)

88991 Adjust plugins and packages .gitignore to be most useful (tool, cla: yes)

89009 Clean up null assumptions in vmservice for null safe migration (tool, cla: yes, waiting for tree to go green, a: null-safety)