Allow soong config variables to be boolean-typed

So that you can use `true` instead of `"true"` in select expressions.

Bug: 323382414
Test: m nothing --no-skip-soong-tests
Change-Id: I950bd8e04f8fab5187ea5075514d476227943f33

android/variable.go

@@ -399,7 +399,8 @@ type ProductVariables struct {
 
 	PlatformSepolicyCompatVersions []string `json:",omitempty"`
 
-	VendorVars map[string]map[string]string `json:",omitempty"`
+	VendorVars     map[string]map[string]string `json:",omitempty"`
+	VendorVarTypes map[string]map[string]string `json:",omitempty"`
 
 	Ndk_abis *bool `json:",omitempty"`