all: use go/parser.SkipObjectResolution in more places
None of cgo, "go test", nor srcimporter make use of go/ast's object
resolution via go/ast.Object. As such, we can skip that work during
parse time, which should save some CPU time.
We don't have any benchmark numbers, as none of the three packages have
any usable benchmarks, but we measured gofmt to be about 5% faster
thanks to this tweak in https://go.dev/cl/401454.
These three packages are quite different to gofmt, but one can expect
similar speed-ups in the 1-5% range.
Two notable exceptions, which do make use of go/ast.Object, are cmd/fix
and cmd/doc - we do not modify those here.