Disable null safety auto-detection for the web

* 53d5d6853 Add dart-lang/sdk's new package:clock dependency (flutter/engine#22142)

* c32e3d8fd Roll Skia from 7737a5bd2510 to 5567a6091ceb (8 revisions) (flutter/engine#22146)

* 376045c00 Roll Fuchsia Linux SDK from XYN02FThN... to UKgKCjxSA... (flutter/engine#22147)

* 03395debd Roll Fuchsia Mac SDK from GKPwGj1Ux... to xHjtLQPQ5... (flutter/engine#22151)

* 0c7e9528a Manual Dart SDK roll 6e015bd9cddb to 9c6e76468ca4 (6 revisions (flutter/engine#22153)

* e5f168a67 Update constraint to latest integration test (flutter/engine#22169)

* e61e8c248 Smooth window resizing on macOS (flutter/engine#21525)

* acece00f0 Allow parse_and_send to use access tokens (flutter/engine#22019)

* 0270632d8 Includes roles for links, checkboxes, and radio buttons in semantics (flutter/engine#22061)

* 632354d96 Roll Fuchsia Linux SDK from UKgKCjxSA... to PY5hNI-wY... (flutter/engine#22175)

* 62d50af37 Add plumbing for command line arguments on Windows (flutter/engine#22094)

* 06b0910e2 Fix possible use of std::moved value in Rasterizer (flutter/engine#22125)

* 005dec449 [web] Clean up unused previousStyle logic (flutter/engine#22150)

* ca05bdccc Roll Skia from 5567a6091ceb to f548a028ce70 (7 revisions) (flutter/engine#22155)

* 5b07ac4c4 Roll Fuchsia Mac SDK from xHjtLQPQ5... to ICK_JlnKJ... (flutter/engine#22188)

* d615a97a1 Roll Fuchsia Linux SDK from PY5hNI-wY... to Usec4YBzR... (flutter/engine#22197)

* 11ed711eb Invalidate the cached SkParagraph font collection when a new font manager is installed (flutter/engine#22157)

* 07c780bd9 [web] Assign default natural width/height for svgs that report 0,0 on firefox and ie11 (flutter/engine#22184)

* b54bb88f0 Migrate runZoned to runZonedGuarded (flutter/engine#22198)

* 247139a8c [web] Fix transform not invalidating path bounds causing debugValidate failure (flutter/engine#22172)

* e4dffc107 [web] Fix scroll wheel line delta on Firefox. (flutter/engine#21928)

* d6627c6a7 Reland [ios] Refactor IOSSurface factory and unify surface creation (flutter/engine#22016)

* ce1dd11f5 Standardize macro names for dartdoc macros (flutter/engine#22180)

* f81bc371c [profiling] Handle thread_info to account for killed threads (flutter/engine#22170)

* fd94c863d Fix for firefox custom clipping (flutter/engine#22182)

* 9ccf9f120 bring back build_test to ensure we validate licenses (flutter/engine#22201)

* 38f6665bd Set strut font to Roboto if the given font hasn't been registered (flutter/engine#22129)

* caf32d5b2 Add a proc table version of embedder API (flutter/engine#21813)

* ed0f477c5 Use preTranslate when applying offset to matrix (flutter/engine#21648)

* b457e2dd8 Refactor make_mock_engine into fl_test (flutter/engine#21585)

* 28497c864 Fix typos in FlValue docs (flutter/engine#21875)

* bb32446c6 Fix FlTextInputPlugin tear down (flutter/engine#22007)

* 7a7804b6d Add "input shield" to capture pointer input for reinjection (flutter/engine#22067)

* fe85f946d Update painting.dart (flutter/engine#22195)

* 99cc50dff [ios] Surface factory holds the canonical reference to the external view embedder (flutter/engine#22206)

Fixes #69348

If the web development server fails to bind, then retry up to 5 times. If a port was not provided, select a new free port each time.

The flutter run failures are cause by the application occasionally taking a long time to start up. This caused the ios fallback discovery to kick in, which will always fail if the application hasn't started. Solution: remove the iOS fallback discovery and wait up to 30 seconds.

This has not proven to reduce the flakes, but it does at least remove one error case and removes code that will no longer work without the mDNS fallback.

This removes the nullOk parameter from Focus.of, FocusTraversalOrder.of and FocusTraversalGroup.of, and creates maybeOf equivalents for each. The of methods now return non-nullable values, and the maybeOf equivalents return nullable values.

This removes the nullOk parameter from AnimatedList.of and SliverAnimatedList.of, and creates maybeOf equivalents for each. The of methods now return non-nullable values, and the maybeOf equivalents return nullable values.

This removes the nullOk parameter from Router.of, and createsRouter.maybeOf. Router.ofnow returns a non-nullable value, and the Router.maybeOf returns a nullable value.

This removes the nullOk parameter from Shortcuts.of, Actions.find and Actions.handler and created Shortcuts.maybeOf and Actions.maybeFind. Shortcuts.of and Actions.find now return non-nullable values, and the maybe versions return a nullable value. I didn't create a non-nullable version of Actions.handler, since it needs to be able to return null if an action is not enabled, but I did remove the nullOk parameter, effectively setting it to true permanently, since setting it to false doesn't make much sense if the function can still return null when the action is not enabled.

Enable web tool integration tests: expression evaluation, stepping, and basic hot restart

Enables build_test for Linux. Currently only flutter_gallery has platform directories for the desktop platforms, so this will run only that build, but this will provide an end-to-end build test for Linux.

Other example/test projects can be brought online for Linux in the future just by adding the linux/ directory to the project.

* [devicelab] work around occasional null values for devtools

* Update perf_tests.dart

This reverts commit d0cdfa41.