feat: add quoteGasPayment to ICA router (#3460)

### Description

- for easier offchain use, we can directly call the ICA router to fetch
the quote needed for the dispatch.

### Drive-by changes

None

### Related issues

None

### Backward compatibility

Yes

### Testing

Unit

solidity/contracts/middleware/InterchainAccountRouter.sol

@@ -656,4 +656,15 @@ contract InterchainAccountRouter is Router {
     ) private view returns (address payable) {
         return payable(Create2.computeAddress(_salt, bytecodeHash));
     }
+
+    /**
+     * @notice Returns the gas payment required to dispatch a message to the given domain's router.
+     * @param _destination The domain of the destination router.
+     * @return _gasPayment Payment computed by the registered hooks via MailboxClient.
+     */
+    function quoteGasPayment(
+        uint32 _destination
+    ) external view returns (uint256 _gasPayment) {
+        return _quoteDispatch(_destination, "");
+    }
 }

solidity/test/InterchainAccountRouter.t.sol

@@ -339,6 +339,18 @@ contract InterchainAccountRouterTest is Test {
         assertEq(ownerBytes, owner.addressToBytes32());
     }
 
+    function test_quoteGasPayment() public {
+        // arrange
+        originRouter.enrollRemoteRouterAndIsm(
+            destination,
+            routerOverride,
+            ismOverride
+        );
+
+        // assert
+        assertEq(originRouter.quoteGasPayment(destination), gasPaymentQuote);
+    }
+
     function testFuzz_singleCallRemoteWithDefault(bytes32 data) public {
         // arrange
         originRouter.enrollRemoteRouterAndIsm(