Use runtime/debug in our changeset package

[dprotaso]

Did some testing - runtime/debug probably won't be super useful until 1.18, particularly for local changes.

The main module info for something built not at a semver tag looks like:

Main:{Path:knative.dev/pkg Version:(devel) Sum: Replace:<nil>}

What we really want are the vcs tags included in 1.18 which look like:

Settings:[
 {Key:-compiler Value:gc}
 {Key:CGO_ENABLED Value:1}
 {Key:CGO_CFLAGS Value:}
 {Key:CGO_CPPFLAGS Value:} 
 {Key:CGO_CXXFLAGS Value:}
 {Key:CGO_LDFLAGS Value:} 
 {Key:GOARCH Value:amd64} 
 {Key:GOOS Value:linux} 
 {Key:GOAMD64 Value:v1} 
 {Key:vcs Value:git} 
 {Key:vcs.revision Value:62b1122c86b2f032117da832332037ff511c2b74} 
 {Key:vcs.time Value:2022-02-11T23:48:33Z} 
 {Key:vcs.modified Value:true}
]

Originally posted by @wlynch in #2425 (comment)

[dprotaso]

We should switch over when we start using go1.18 for building

[github-actions]

This issue is stale because it has been open for 90 days with no
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inactivity. Reopen the issue with /reopen. Mark the issue as
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[dprotaso]

/lifecycle frozen