Sync .packages file as a normal input file. (#16467)
Sync .packages file as a normal input file. (#16467)

* Sync .packages file as regular file.

Currently .packages file is treated specially as DevFSStringContent to accommodate package-file rewrite when it is sent to the device for dart1 compilation. In dart2 we need to treat .packages as regular file because from frontend perspective it's just a normal input file.
tvolkert/flutter,Hixie/flutter,cbracken/flutter,Hixie/flutter,Hixie/flutter,tvolkert/flutter,Hixie/flutter,cbracken/flutter,cbracken/flutter,cbracken/flutter,flutter/flutter,Hixie/flutter,Hixie/flutter,flutter/flutter,flutter/flutter,Hixie/flutter,tvolkert/flutter,flutter/flutter,cbracken/flutter,flutter/flutter,tvolkert/flutter,tvolkert/flutter,tvolkert/flutter,Hixie/flutter,tvolkert/flutter,flutter/flutter,cbracken/flutter,Hixie/flutter,flutter/flutter,flutter/flutter,cbracken/flutter,Hixie/flutter,cbracken/flutter,cbracken/flutter,flutter/flutter,tvolkert/flutter,tvolkert/flutter,flutter/flutter,cbracken/flutter,tvolkert/flutter