* Reland "Roll engine to version b148e628ec86b3a9a0382e0bcfae73f0390a8232 (#20427)"
This is a re-land with downgraded `package:flutter_gallery_assets`
version.
* Downgrade package:flutter_gallery_assets to 0.1.4
* Change engine.version to 81baff97c29bb08cbf8453a3f9042c5813f84ad3 (which contains an additional fix)
* Change engine.version to e3687f70c7ece72000b32ee1b3c02755ba5361ac (since mac tarballs are corrupted on earlier commit)
Reason for revert: The package:flutter_gallery_assets has removed some images which are required for the examples/flutter_gallery, so the gallery build is failing (only discovered after landing, since gallery doesn't seem to get built during github PR presubmit checks)
This CL
* rolls `engine.version` to flutter/engine@b148e628 (which includes dart sdk 2.1.0-dev)
* rolls `goldens.version` to flutter/goldens@6c45fafdf (which includes updates due to skia changes in engine)
* changes `platform.dill` to `platform_strong.dill` in various places due to flutter/engine@a84b210b
* adds explicit `environment: sdk: ">=2.0.0-dev.68 < 3.0.0"` constraints to `pubspec.yaml` and `pubspec.yaml.tmpl` files (since pub defaults to `<2.0.0` if omitted)
* upgrades to newer versions of various 3rd party packages (to ensure transitive dependencies have `<3.0.0` sdk constraint)
When creating a new project, the build fails with an error similar to:
"versionCode not found. Define flutter.versionCode in the local.properties file."
This puts developers in the untenable situation of having to edit a file with local paths, but being unable to check it in.
This changes the templates to default to using versionCode 1 and version "1.0" if they are not defined in the local.properties file.
Fixes#18983.
Generated.xcconfig is only required at build time for iOS apps. In the
flutter create project template and example apps, Generated.xcconfig was
previously marked as a resource to be bundled into the built app.
Uses the `version` property from the `pubspec.yaml` file to set the corresponding fields in the `local.properties` file respectively in the `Generated.xcconfig` file.
The `--build-name` and `--build-number` options have changed. Now they trump the `version` property from the `pubspec.yaml` file.
If the `version` property is not set and the `--build-name` and `--build-number` options are not provided, the build command will not change the `local.properties` / `Generated.xcconfig` file.
Dart is migrating to .dart_tool/ as the location for cached artifacts
and other temporary files generated by tooling in the SDK. As part of
this, pub will be migrating from .pub to .dart_tool/pub.
In future, this path will also be used for other tooling, such as package:build.
