Update min_sdk_version from SdkSpec to ApiLevel

min_sdk_version signifies device version and does not need an sdkKind to
describe it fully. Update the type and cleanup existing usages. As a
side benefit, we also get better error handling since users can no
longer enter something like `public_30` as a valid min_sdk_version in bp
files

Will do a similar cleanup for targetSdkVersion and maxSdkVersion in a
followup CL

Test: m nothing
Test: no change in ninja files (this should be a no-op)
Bug: 208456999

Change-Id: Ie6ae7e267d093c5e4787e82685daaca1021d202e
diff --git a/apex/builder.go b/apex/builder.go
index ee6c473..45c5267 100644
--- a/apex/builder.go
+++ b/apex/builder.go
@@ -1063,10 +1063,10 @@
 		} else {
 			toMinSdkVersion := "(no version)"
 			if m, ok := to.(interface {
-				MinSdkVersion(ctx android.EarlyModuleContext) android.SdkSpec
+				MinSdkVersion(ctx android.EarlyModuleContext) android.ApiLevel
 			}); ok {
-				if v := m.MinSdkVersion(ctx); !v.ApiLevel.IsNone() {
-					toMinSdkVersion = v.ApiLevel.String()
+				if v := m.MinSdkVersion(ctx); !v.IsNone() {
+					toMinSdkVersion = v.String()
 				}
 			} else if m, ok := to.(interface{ MinSdkVersion() string }); ok {
 				// TODO(b/175678607) eliminate the use of MinSdkVersion returning
@@ -1087,7 +1087,7 @@
 		return !externalDep
 	})
 
-	a.ApexBundleDepsInfo.BuildDepsInfoLists(ctx, a.MinSdkVersion(ctx).Raw, depInfos)
+	a.ApexBundleDepsInfo.BuildDepsInfoLists(ctx, a.MinSdkVersion(ctx).String(), depInfos)
 
 	ctx.Build(pctx, android.BuildParams{
 		Rule:   android.Phony,