Imports of test2json command

PathSynopsis
cmd/internal/test2jsonPackage test2json implements conversion of test binary output to JSON.
flagPackage flag implements command-line flag parsing.
fmtPackage fmt implements formatted I/O with functions analogous to C's printf and scanf.
internal/execabs
ioPackage io provides basic interfaces to I/O primitives.
osPackage os provides a platform-independent interface to operating system functionality.