style: gofumpt all the things (#9829)

Literally `gofumpt -w .` from the top level dir. Guaranteed to be minor
style changes only and nothing else.

@imsodin per request?

lib/osutil/atomic_unix_test.go

@@ -38,7 +38,7 @@ func TestTempFilePermissions(t *testing.T) {
 	// The temp file should have 0600 permissions at the most, or we have a
 	// security problem in CreateAtomic.
 	t.Logf("Got 0%03o", info.Mode())
-	if info.Mode()&^0600 != 0 {
+	if info.Mode()&^0o600 != 0 {
 		t.Errorf("Permission 0%03o is too generous", info.Mode())
 	}
 }