Plugins: Make it possible to support multiple plugin versions (#82116)

* first pass

* use version in more places

* add comment

* update installer

* fix wire

* fix tests

* tidy

* simplify changes

* fix in mem

* remove unused step

* fix step dupe logic for child plugins + add tests

pkg/services/pluginsintegration/loader/loader_test.go

@@ -1666,7 +1666,7 @@ func verifyState(t *testing.T, ps []*plugins.Plugin, reg registry.Service,
 	t.Helper()
 
 	for _, p := range ps {
-		regP, exists := reg.Plugin(context.Background(), p.ID)
+		regP, exists := reg.Plugin(context.Background(), p.ID, p.Info.Version)
 		require.True(t, exists)
 		if !cmp.Equal(p, regP, compareOpts...) {
 			t.Fatalf("Result mismatch (-want +got):\n%s", cmp.Diff(p, regP, compareOpts...))