Convert more versions in config to ApiLevel.

The test case I removed is invalid. The codename has had its int
assigned, but the config claims it is not final.

If this ever does need to be supported it's just a matter of making
sure the Q -> 29 mapping (or whatever) in the finalized codenames map
in android/api_levels.go.

Test: treehugger
Bug: http://b/154667674
Change-Id: I4f42ec2fd4a37750519ee3937938a1c65b6bb1e8
diff --git a/apex/prebuilt.go b/apex/prebuilt.go
index 37457e9..9f6c8ad 100644
--- a/apex/prebuilt.go
+++ b/apex/prebuilt.go
@@ -326,7 +326,7 @@
 			Args: map[string]string{
 				"abis":              strings.Join(java.SupportedAbis(ctx), ","),
 				"allow-prereleased": strconv.FormatBool(proptools.Bool(a.properties.Prerelease)),
-				"sdk-version":       ctx.Config().PlatformSdkVersion(),
+				"sdk-version":       ctx.Config().PlatformSdkVersion().String(),
 			},
 		})