Introduce the NonFungibleTokensV1_1 amendment:

The XLS-20 implementation contained two bugs that would require the
introduction of amendments. This complicates the adoption of XLS-20
by requiring a staggered amendment activation, first of the two fix
amendments, followed by the `NonFungibleTokensV1` amendment.

After consideration, the consensus among node operators is that the
process should be simplified by the introduction of a new amendment
that, if enabled, would behaves as if the `NonFungibleTokensV1` and
the two fix amendments (`fixNFTokenDirV1` and `fixNFTokenNegOffer`)
were activated at once.

This commit implements this proposal; it does not introduce any new
functionality or additional features, above and beyond that offered
by the existing amendments.

src/test/app/NFTokenDir_test.cpp

@@ -1075,7 +1075,8 @@ public:
     {
         using namespace test::jtx;
         FeatureBitset const all{supported_amendments()};
-        FeatureBitset const fixNFTDir{fixNFTokenDirV1};
+        FeatureBitset const fixNFTDir{
+            fixNFTokenDirV1, featureNonFungibleTokensV1_1};
 
         testWithFeats(all - fixNFTDir);
         testWithFeats(all);