This PR improves the gen_defaults tests to not be tied to a particular order of execution.
Since there is a global class that holds the state of the used/not used tokens, we need to clear this logger before each test.
Fixes https://github.com/flutter/flutter/issues/142716
cc @zanderso @QuncCccccc
*If you had to change anything in the [flutter/tests] repo, include a link to the migration guide as per the [breaking change policy].*
d242d1368f