Update rule index's trie node scalars to use custom map

Earlier the trie's scalar used map[ast.Value]trieNode.
This resulted in unexpected key comparison results such
as 1 != 1.0 when key types were ast.Number for example.
This change updates the scalar to use a util.HashMap instead
that will utilize ast.Compare to perfom key comparisons.

Fixes: #5585

Signed-off-by: Ashutosh Narkar <anarkar4387@gmail.com>