Nuke old singlepass compiler, enable optimizing compiler by default (#2130)

Signed-off-by: Takeshi Yoneda <t.y.mathetake@gmail.com>

builder_test.go

@@ -308,9 +308,7 @@ func TestNewHostModuleBuilder_Compile(t *testing.T) {
 		tc := tt
 
 		t.Run(tc.name, func(t *testing.T) {
-			cfg := NewRuntimeConfig()
-			cfg.(*runtimeConfig).EnableOptimizingCompiler()
-			b := tc.input(NewRuntimeWithConfig(testCtx, cfg)).(*hostModuleBuilder)
+			b := tc.input(NewRuntime(testCtx)).(*hostModuleBuilder)
 			compiled, err := b.Compile(testCtx)
 			require.NoError(t, err)
 			m := compiled.(*compiledModule)