CNDB-141284: use ByteBuffer.remaining instead of limit to asset size (#1755)

The data inserted into the trie in `TrieMemoryIndex` is `encodedTerm`,
which is built from `term` and only on the "available" bytes (between
`term.position()` and `term.limit()`). But the check that decides to use
the (more efficient) recursive path or not uses `term.limit()` to assess
the size of `encodedTerm`. If `term.position()` is not 0, this is
incorrect, and can lead to using the less optimal pass completely
unecessarily. This has been shown to happen when investigating
riptano/cndb#14153: the non-recursive path was
taken even for boolean values (because the nodes were using
`offheap_buffers`; with `offheap_objects`, the buffers getting to
`TriMemoryIndex` are 0-positioned).

See riptano/cndb#14184.

Author: pcmanus

src/java/org/apache/cassandra/index/sai/memory/TrieMemoryIndex.java

@@ -252,7 +252,7 @@ private void applyTransformer(PrimaryKey primaryKey,
 
                 try
                 {
-                    data.putSingleton(encodedTerm, primaryKey, transformer, term.limit() <= MAX_RECURSIVE_KEY_LENGTH);
+                    data.putSingleton(encodedTerm, primaryKey, transformer, term.remaining() <= MAX_RECURSIVE_KEY_LENGTH);
                 }
                 catch (TrieSpaceExhaustedException e)
                 {