Move tools tests into a general.shard directory in preparation to changing how we shard tools tests (#36108)

* enable lint unnecessary_new

* fix tests

* fix tests

* fix tests

* Upgrade everything except matcher.
* Roll matcher (and test)
* Adjust tests that depend on flutter:test directly to depend on a shim
* Require use of package:test shim and remove other references to package:test

* Remove uses of deprecated constants
* Change int.parse to int.tryParse where appropriate

The new values are not ready for use yet inside Google

* Roll engine to e976be13c51448f89107d082ec81e2b6731671fa

* move away from deprecated constants

* Change async stubbing to use thenAnswer.

Mockito now prohibits calling thenReturn with Futures and Streams. dart-lang/mockito#79

* Update all Mockito deps to 3.0.0.

* Revert "Update all Mockito deps to 3.0.0."

This reverts commit e8ab9d37c33d3d7fe384abde64ea5b4d72623c75.

I did not correctly update the mockito dep, and there's no easy way to update to 3.0 alpha right now.

* Change thenAnswer((_) => to thenAnswer((invocation) =>

* Add Invocation type to thenAnswer lambdas

* Make ProcessSignals portable

This removes the need to wrap unsupported signals with in `if (!platform.isWindows) ..`.

It also allows us to implement a work around for breaking the Windows console when flutter is exited with Ctrl+C.

* review comments

* adding tests

* add license header