Rename Q8 microkernels and operators to QU8

- Indicate unsigned datatype
- Make space for QS8 with signed quantization

PiperOrigin-RevId: 321275708
diff --git a/test/fully-connected-operator-tester.h b/test/fully-connected-operator-tester.h
index b1d4f76..64f9d39 100644
--- a/test/fully-connected-operator-tester.h
+++ b/test/fully-connected-operator-tester.h
@@ -129,7 +129,7 @@
     return this->iterations_;
   }
 
-  void TestQ8() const {
+  void TestQU8() const {
     std::random_device random_device;
     auto rng = std::mt19937(random_device());
     auto s32rng = std::bind(std::uniform_int_distribution<int32_t>(-10000, 10000), rng);
@@ -204,7 +204,7 @@
       xnn_operator_t fully_connected_op = nullptr;
 
       ASSERT_EQ(xnn_status_success,
-        xnn_create_fully_connected_nc_q8(
+        xnn_create_fully_connected_nc_qu8(
           input_channels(), output_channels(),
           input_stride(), output_stride(),
           input_zero_point, 1.0f /* input scale */,
@@ -218,7 +218,7 @@
       std::unique_ptr<xnn_operator, decltype(&xnn_delete_operator)> auto_fully_connected_op(fully_connected_op, xnn_delete_operator);
 
       ASSERT_EQ(xnn_status_success,
-        xnn_setup_fully_connected_nc_q8(
+        xnn_setup_fully_connected_nc_qu8(
           fully_connected_op,
           batch_size(),
           input.data(), output.data(),