Fix RowColumnOracle Signature (#1780)

The row and column oracle are defined as such ([Lin Lin (2022). Ch.
6.5.](https://arxiv.org/abs/2201.08309)):
$O_c\ket{\ell}\ket{j}=\ket{c(j, \ell)}\ket{j}$, where $c(j,\ell)$ gives
the $\ell$-th non zero entry in the $j$-th column.

So indeed, in input the value of l is bounded by the number of non zero
entries in the matrix. But in output, the value of $c(j,\ell)$ is
unbounded as the $\ell$-th non zero entry can be anywhere in the column.

So the Signature of `RowColumnOracle` is incorrect and that was making
`assert_consistent_classical_action` throwing errors it should not have.

This is fixed by this PR.

Co-authored-by: Matthew Harrigan <mpharrigan@google.com>

Author: petim0

qualtran/bloqs/block_encoding/sparse_matrix.py

@@ -33,6 +33,7 @@
     QInt,
     QUInt,
     Register,
+    Side,
     Signature,
     Soquet,
     SoquetT,
@@ -94,8 +95,12 @@ def __attrs_post_init__(self):
 
     @cached_property
     def signature(self) -> Signature:
-        return Signature.build_from_dtypes(
-            l=BQUInt(self.system_bitsize, self.num_nonzero), i=QUInt(self.system_bitsize)
+        return Signature(
+            [
+                Register("l", BQUInt(self.system_bitsize, self.num_nonzero), side=Side.LEFT),
+                Register("l", QUInt(self.system_bitsize), side=Side.RIGHT),
+                Register("i", QUInt(self.system_bitsize)),
+            ]
         )