v.io/x/ref/lib/exec: Use verror instead of errors.New() and fmt.Errorf()
The CL replaces uses of fmt.Errorf() and errors.New() in v.io/x/ref/lib/exec
with verror. Various other things change as modules (especially in profiles)
were testing against the format strings.
Error messagews were changed as little as possible, usually just adding "{1:}{2:} ".
The error errFailedStatus in v.io/x/ref/lib/exec/parent.go merits
special review because there is no actual text in the error message.
The previous code went to some trouble to remove some text from the message,
leaving only a parameter string. I did the same.
Tested:
cd v.io
v23 go test ./...
v23 test run vanadium-go-test
Change-Id: If20378a55175250abbfc5775c4b3768cb646bbec
11 files changed
