* Unskip integration tests on Windows that now pass

The referenced issue is closed and these tests pass for me locally on Windows now.

* Remove import that's no longer used

* Add another issue that is afffecting these tests on Windows

* Add a hot restart test and mark skip on Windows

Skipped due to https://github.com/flutter/flutter/issues/21348.

* Unskip expression evaluation integration tests for non-Windows

* Add additional into to skip comments

* Add missing import

Due to CPU contention we've seen these go really slow on Cirrus (see https://github.com/flutter/flutter/issues/19542#issuecomment-414265152), and there's also a chance our flakes are timeouts due to running slow rather than hanging.

All temporary directory start with `flutter_` and have their random component separated from the name by a period, as in `flutter_test_bundle.YFYQMY`.

I've tried to find some of the places where we didn't cleanly delete temporary directories, too. This greatly reduces, though it does not entirely eliminate, the directories we leave behind when running tests, especially `flutter_tools` tests.

While I was at it I standardized on `tempDir` as the variable name for temporary directories, since it was the most common, removing occurrences of `temp` and `tmp`, among others.

Also I factored out some common code that used to catch exceptions that happen on Windows, and made more places use that pattern.

* 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

* Rename util -> test_utils

* Rename flutter_test_driver -> test_driver

* Switch testWithContext -> test

* Remove unused import

* Move test project into a class to make it easier to have multiple of these

Each "TestProject" class can contain its files and things like named breakpoint locations.

* Split expression evaluation tests into own file

* Include last response in error messages

* Update expectations based on current bugs

* Fix async-ness in tests

* Fix incorrect expectation in test

* Fix incorrect evaluations

* Remove skips for tests that are now passing on master

* Expect pass on Linux

‍♂️

* Call the code

* Skip expression evaluation tests on Windows

* Skip whole group, not just one test

* Remove duplicated method from merge

* Fix misplaced close of group

* Remove code that was duplicated from test we copied

Not sure how this ended up in here?

* Re-fix typo