* Start logger in startProgress to avoid assertion failure
There are lots of places that create a Status() and all but two of them call ..start() immediately. This is one of the places that doesn't, which causes an assertion failure when running with --enable-asserts and the other is in the same file (I suspect it's also incorrect, but possibly it's never used - I'll look at that separately when I can trace some code that calls it).
Fixes#20812.
* Enable asserts for tools tests
* Fix lint
* Rename enableAsserts -> enableFlutterToolAsserts
To make it clearer that it only enables asserts for flutter_tools when set.
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