Deprecate VelocityTracker default constructor and added VelocityTracker.withKind constructor (#66043)

We've gotten feedback that the VelocityTracker change was disruptive, though it did not break any of the flutter framework or customer tests. In order to make the change non-breaking, PointerDeviceKind parameter can be made optional.

Nevertheless, this parameter should be provided so that the existing touch handlers can use more accurate gestures on mouse/stylus inputs, so we can encourage this by deprecating the default constructor and pointing users towards the VelocityTracker.withKind constructor that takes a non-optional parameter

Currently the framework uses fairly large "hit slop" values to disambiguate taps from drags/pans. This makes sense on touch devices where the interaction is not very precise, on mice however it can feel as if the UI is lagging. This is immediately noticeable on our infra dashboard, where it takes almost half of a grid square of drag before the actual drag kicks in.

One potential solution is to always use smaller constants depending on whether the interaction is mouse or touch based. The only reasonable choice is to use the pointer device kind and not target platform - same platform can have different input sources. This requires exposing the pointer device kind in a few new places in several of the gesture detectors, and using the enum to compute the correct hit slop from an expanded set of constants.

This almost works, however there are a few places (notably ListViews) which uses the touch hit slop as a default value in scroll physics. It does not seem like it will be easy to disambiguate a user provided scroll physics constant from the default and/or adjust it somehow - this might require significant changes to scroll physics which I have left out of this PR.

This PR does not adjust:

kTouchSlop used in scroll_physics.dart's minFlingDistance
kTouchSlop used in PrimaryPointerGestureRecognizer/LongPressGestureRecognizer

* Update project.pbxproj files to say Flutter rather than Chromium

Also, the templates now have an empty organization so that we don't cause people to give their apps a Flutter copyright.

* Update the copyright notice checker to require a standard notice on all files

* Update copyrights on Dart files. (This was a mechanical commit.)

* Fix weird license headers on Dart files that deviate from our conventions; relicense Shrine.

Some were already marked "The Flutter Authors", not clear why. Their
dates have been normalized. Some were missing the blank line after the
license. Some were randomly different in trivial ways for no apparent
reason (e.g. missing the trailing period).

* Clean up the copyrights in non-Dart files. (Manual edits.)

Also, make sure templates don't have copyrights.

* Fix some more ORGANIZATIONNAMEs

* Add semanticsEnabled to widgetBenchmark
* Add button_matrix_app and gesture benchmark

This is a re-land of #31561, after fixing performance regressions.

Added change listening to the MouseTracker so that the Listener and tooltip can react to whether or not a mouse is connected at all. Added a change check to make sure Listener only repaints when something changed.

Fixes #22817

* add trailing commas on list/map/parameters

* add trailing commas on Invocation with nb of arg>1

* add commas for widget containing widgets

* add trailing commas if instantiation contains trailing comma

* revert bad change

* enable lint unnecessary_new

* fix tests

* fix tests

* fix tests

It was causing problems rolling Flutter into Fuchsia

* re-enable lint unnecessary_const

* remove trailling whitespaces

* remove unnecessary const (after merge)

This reverts commit cc1cf13e.

* Manually fix every use of Point.x and Point.y

Some of these were moved to dx/dy, but not all.

* Manually convert uses of the old gradient API

* Remove old reference to Point.

* Mechanical changes

I applied the following at the root of the Flutter repository:

git ls-files -z | xargs -0 sed -i 's/\bPoint[.]origin\b/Offset.zero/g'
git ls-files -z | xargs -0 sed -i 's/\bPoint[.]lerp\b/Offset.lerp/g'
git ls-files -z | xargs -0 sed -i 's/\bnew Point\b/new Offset/g'
git ls-files -z | xargs -0 sed -i 's/\bconst Point\b/const Offset/g'
git ls-files -z | xargs -0 sed -i 's/\bstatic Point /static Offset /g'
git ls-files -z | xargs -0 sed -i 's/\bfinal Point /final Offset /g'
git ls-files -z | xargs -0 sed -i 's/^\( *\)Point /\1Offset /g'
git ls-files -z | xargs -0 sed -i 's/ui[.]Point\b/ui.Offset/g'
git ls-files -z | xargs -0 sed -i 's/(Point\b/(Offset/g'
git ls-files -z | xargs -0 sed -i 's/\([[{,]\) Point\b/\1 Offset/g'
git ls-files -z | xargs -0 sed -i 's/@required Point\b/@required Offset/g'
git ls-files -z | xargs -0 sed -i 's/<Point>/<Offset>/g'
git ls-files -z | xargs -0 sed -i 's/[.]toOffset()//g'
git ls-files -z | xargs -0 sed -i 's/[.]toPoint()//g'
git ls-files -z | xargs -0 sed -i 's/\bshow Point, /show /g'
git ls-files -z | xargs -0 sed -i 's/\bshow Point;/show Offset;/g'

* Mechanical changes - dartdocs

I applied the following at the root of the Flutter repository:

git ls-files -z | xargs -0 sed -i 's/\ba \[Point\]/an [Offset]/g'
git ls-files -z | xargs -0 sed -i 's/\[Point\]/[Offset]/g'

* Further improvements and a test

* Fix minor errors from rebasing...

* Roll engine

* Return null from VM.mainView if no view exists
* Retry in connectToServiceProtocol if a view is not yet available
* Do not explicitly call exit from the benchmarks - it will not cleanly shut down the engine

Our microbenchmarks now run on real devices.