66980 [flutter_tools] fix documentation, globals, and todos in the android codebase (cla: yes, tool)

66983 [flutter_tools] prevent running analyze-size with split-debug-info (cla: yes, tool)

66995 [flutter_tool] enable single widget reload optimization by default on dev (cla: yes, tool, waiting for tree to go green)

66997 Fix Windows and Linux plugin template filenames (cla: yes, tool, waiting for tree to go green)

67012 Replace MockArtifacts with Artifacts.test() (cla: yes, team, tool)

67019 Replace MockProcessManager with FakeProcessManager (cla: yes, team, tool, waiting for tree to go green)

67029 Improve Windows symlink instructions (a: build, a: desktop, cla: yes, platform-windows, tool)