* Switch to URIs for breakpoints and unskip tests on Windows

addBreakpointWithScriptUri expects Uris. By coincidence, FS paths work on Mac/Linux but they fail on Windows. One of the issues in the skip comment is fixed, the other one seems not relevant here.

* Apply symlink resolution to all integration tests

The default temp folders we get include symlinks which breaks breakpoints.

* Save 

* Fix typo

This reverts commit a34488dd.

aed6b8c46 Roll Dart to ac6d4f7e653deba11d4836768376537893a9e9d6. (#6549)
3ba6270b2 Roll src/third_party/skia 921ec976556c..4b7b2ceb4ad9 (14 commits) (#6550)

* enable lint unnecessary_new

* fix tests

* fix tests

* fix tests

* 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

* Skip tests instead of expecting failure, because expected failure = timeout which is slow

Some of these tests are known to fail and were coded to expect it; however because the failure is a timeout it's just dragging out test runs (shortening timeouts will make the tests flakier).

* Make it easier to find skipped tests

* Change SKIP to TODO

It was causing problems rolling Flutter into Fuchsia

* Skip integration tests that use flutter-tester on Windows

This is known to be broken. I will un-skip all of these once a fix for flutter-tester lands on Windows.

* Save with added import!

* Add tests to ensure flutter run does not quit at startup

These tests require https://github.com/dart-lang/vm_service_client/pull/38 to be merged and currently the third test (pause-on-exceptions) fails because of a bug.

* Remove TODO

Probably makes most sense this way for now.

* Address PR comments