This adds and enables a raft of new analysis options for the flutter repository, many of which are commented out until we clean up our code and/or address any linter false positives.
This aligns the comments and fixes some misspellings in the three related analysis options files.
There will be a follow on PR with more controversial changes to the repo level analysis options.
This updates the flutter analyze command to use the .analysis_options_flutter_analyze in the repo root when either the --flutter-repo flag is supplied or the sources being analyzed reside in the flutter repo.
* Move global analysis options file to the repo root
Also restore the analysis options file for stocks example, since
the global options trigger warnings on generated intl files.
* Remove obsolete analysis options file for Material Gallery example
