Add support for /product-services partition

This is an adaptation of Icc4f8c16bc389fe20db680849f311d02df1299c3, to
support modules that are installed on the /product-services partition.

Bug: 80741439
Test: m -j both with and without enabling the new partition
Change-Id: I72b335ad38baff5848cd3da7489343f8cf98ff16

android/config.go

@@ -763,6 +763,13 @@ func (c *deviceConfig) ProductPath() string {
 	return "product"
 }
 
+func (c *deviceConfig) ProductServicesPath() string {
+	if c.config.productVariables.ProductServicesPath != nil {
+		return *c.config.productVariables.ProductServicesPath
+	}
+	return "product-services"
+}
+
 func (c *deviceConfig) BtConfigIncludeDir() string {
 	return String(c.config.productVariables.BtConfigIncludeDir)
 }