[flutter_tools] refactor drive launch into separate service, split by mobile+desktop and web (#68451)

Overhaul of flutter drive in order to deliver a better experience, namely:

flutter run and flutter drive now share more flags, so code paths that were previously only testable on run are now testable on drive.
Removes web-initialize-platform as this is no longer used
flutter drive correctly sets up a logger that shows native exceptions, by connecting to the vm service.
VM service connection now provides access to memory info without launching devtools (only for debug/profile mode)
Web changes

Passes on the one test in the repo, otherwise the webdriver code has been isolated as much as possible

Additional NNBD related bug fixes:

No longer passes --enable-experiment to the test script. (FYI @blasten ). earlier we might have assumed that the flutter gallery benchmarks would be migrated along side the app and flutter driver, but only the app under test needs to be migrated. The test scripts should never be run with the experiment.