Retain all stubs versions in the snapshot.

This is a quick fix to avoid build failures due to prebuilts lacking
stubs versions that the sources have, which causes dependencies on
older version stubs fail on master-art-host where the sources of e.g.
Bionic are no longer available.

More work is required to make the version handling of stubs DTRT - a
TODO comment outlines it.

Test: m nothing
Test: `m runtime-module-sdk`, check that the generated Android.bp
  has the full stubs.versions list like the sources.
Bug: 169373910
Change-Id: I0ebfaf94f9d45a0e58d9785c40e7cea626f0ab83

sdk/cc_sdk_test.go

@@ -2330,7 +2330,11 @@ cc_prebuilt_library_shared {
     installable: false,
     compile_multilib: "both",
     stubs: {
-        versions: ["3"],
+        versions: [
+            "1",
+            "2",
+            "3",
+        ],
     },
     arch: {
         arm64: {
@@ -2347,7 +2351,11 @@ cc_prebuilt_library_shared {
     prefer: false,
     compile_multilib: "both",
     stubs: {
-        versions: ["3"],
+        versions: [
+            "1",
+            "2",
+            "3",
+        ],
     },
     arch: {
         arm64: {
@@ -2401,7 +2409,11 @@ cc_prebuilt_library_shared {
     installable: false,
     compile_multilib: "both",
     stubs: {
-        versions: ["3"],
+        versions: [
+            "1",
+            "2",
+            "3",
+        ],
     },
     target: {
         host: {
@@ -2431,7 +2443,11 @@ cc_prebuilt_library_shared {
     host_supported: true,
     compile_multilib: "both",
     stubs: {
-        versions: ["3"],
+        versions: [
+            "1",
+            "2",
+            "3",
+        ],
     },
     target: {
         host: {