75027 [flutter_tools] switch dart defines to base64 to avoid windows control characters (cla: yes, tool)

75029 Migrate off e2e (cla: yes, team, tool, waiting for tree to go green)

75044 Replace MockConfig with TestConfig (cla: yes, team, tool, waiting for tree to go green)

75160 [flutter_tools] skip web renderer defines unless web target is picked (cla: yes, tool)

75170 Replace context FakeUsage with TestUsage (cla: yes, team, tool)

75209 [gen-l10n] Fixes named and positional parameter issue with NumberFormat when type is specified (a: internationalization, cla: yes, tool, waiting for tree to go green)