In Run API, take a program path and args array, not a script

- add 'env' flag to wsh
- in wsh and wshd, handle short reads from recvmsg
- [#74181678]

Signed-off-by: Max Brunsfeld <mbrunsfeld@pivotallabs.com>
Remove unnecessary copying when reading/writing over socket

Signed-off-by: Max Brunsfeld <mbrunsfeld@pivotallabs.com>