Artifacts from local engine builds will be found based on the --local-engine flag

Host tools can be found in the artifact cache directory for the host platform.
If a developer wants to use a local engine build instead, then provide an
--engine-build flag that selects the specific engine build variant.

* use vendored dart sdk; check the expected version of flutter

* search up directories looking for the flutter root

Update flutter_tools for the "unoptimized" engine build flag and the new output directory naming scheme (#3832)

* avoid sending analytics on ci systems

* review comments

* make the usage text more visible

* update the look of the usage text

* fix analysis errors

* review comments; fix test

* re-add an export for debugPrint

Also update the engine to a build where these tools have been uplaoded

* add google analytics

* send in the run target type

* track device type targets

* use the real GA code

* review comments

* rev to usage 2.0

* rev to 2.2.0 of usage; add tests

* review comments

This is currently hidden for development use.  It will select artifacts from
the android_{Debug,Release}_Deploy output in a local engine build.

* rename the --develop option to --debug

* fail if both --debug and --deploy are specified

* use the new cache code to locate more artifacts

* add todo

* review comments

* find all repo packages

* .dartignore

* run pub for analyze and test

* don't run pub when doing repo analysis

* move logic for when to run pub into the commands

* re-write ternary expression

* more terse flutter upgrade

* fix an issue when updating and the engine update code has changed

* call flutter precache; add a --no-color hidden option

* fix a lint related to getters/setters

* add a target for android-x64

* update armeabi-v7a to x86_64

Do not check for an existing package map if a command is going to run "pub get" to update the package map (#3202)

Also remove a redundant check for the --pub option in the run command

* move the engine download code to dart

* fix populating the bin/cache/pkg dir

* add cache.dart to help manage the cache dir

* sp

The .packages file is replacing the packages directory of symlinks.

All artifacts for iOS are universal.