Add min_sdk_version to android_library_import modules

pom2bp now inserts a min_sdk_version into android_library_import
modules.

Bug: 110848854
Test: m checkbuild
Change-Id: I1396eabd8bfa02755c829ddac03022ffb7a5673e

java/aar.go

@@ -337,6 +337,7 @@ type AARImportProperties struct {
 	Aars []string
 
 	Sdk_version     *string
+	Min_sdk_version *string
 
 	Static_libs []string
 	Libs        []string
@@ -362,6 +363,9 @@ func (a *AARImport) sdkVersion() string {
 }
 
 func (a *AARImport) minSdkVersion() string {
+	if a.properties.Min_sdk_version != nil {
+		return *a.properties.Min_sdk_version
+	}
 	return a.sdkVersion()
 }