cmd/go: support "-x" in most of go mod commands

[hyangah]

https://golang.org/cl/208558 surfaces "-x" flag support in go mod download.
We think "-x" may make sense for most of other go mod commands that involve non-trivial commands execution underneath.

@jayconrod @bcmills

[gopherbot]

Change https://golang.org/cl/208558 mentions this issue: cmd/go: enable -x in go mod download

[gopherbot]

Change https://golang.org/cl/350829 mentions this issue: cmd/go: enable -x in go mod download

[gopherbot]

Change https://go.dev/cl/448915 mentions this issue: cmd/go: enable -x in go mod tidy

[gopherbot]

Change https://go.dev/cl/448935 mentions this issue: cmd/go: enable -x in go mod graph

[gopherbot]

Change https://go.dev/cl/620735 mentions this issue: cmd/go: enable -x in go mod vendor