Set min_sdk_version to be part of mainline modules

Modules contributing mainline modules (APK/APEX) should set
min_sdk_version as well as apex_available.

For now setting min_sdk_version doesn't change build outputs.
But build-time checks will be added soon.

Bug: 152655956
Test: m
Merged-In: Iab1437027fcbe4b7876207ec7605a765ba667b52
Change-Id: Iab1437027fcbe4b7876207ec7605a765ba667b52
(cherry picked from commit b1e43a9005bbd7da00474eb1117ecfa2bedc8da1)
diff --git a/Android.bp b/Android.bp
index ce4214e..72c924f 100644
--- a/Android.bp
+++ b/Android.bp
@@ -26,6 +26,7 @@
             ],
         },
     },
+    min_sdk_version: "29",
 
 }
 
@@ -59,4 +60,5 @@
             exclude_shared_libs: ["libvndksupport"],
         },
     },
+    min_sdk_version: "29",
 }