Refactor requantization in scalar QS8/QC8/QU8 microkernels

- Rename MAGIC variant to FMAGIC (floating-point min/max + magic bias) and
LRINT variant to LRINTF
- Avoid undefined behaviour in LRINT-variant microkernels
- Remove scalar microkernels with RNDNU requantization as they don't properly
handle requantization scale greater than 1.0

PiperOrigin-RevId: 419542667
diff --git a/test/qs8-igemm-minmax-fp32.yaml b/test/qs8-igemm-minmax-fp32.yaml
index 5c27d55..d81de8c 100644
--- a/test/qs8-igemm-minmax-fp32.yaml
+++ b/test/qs8-igemm-minmax-fp32.yaml
@@ -499,51 +499,51 @@
 - name: xnn_qs8_igemm_minmax_fp32_ukernel_3x4c8__wasmsimd_mul16_ld128
   init: xnn_init_qs8_conv_minmax_fp32_wasmsimd_params
   k-block: 8
-- name: xnn_qs8_igemm_minmax_fp32_ukernel_1x2__scalar_lrint
-  init: xnn_init_qs8_conv_minmax_fp32_scalar_lrint_params
+- name: xnn_qs8_igemm_minmax_fp32_ukernel_1x2__scalar_lrintf
+  init: xnn_init_qs8_conv_minmax_fp32_scalar_lrintf_params
   k-block: 1
-- name: xnn_qs8_igemm_minmax_fp32_ukernel_2x2__scalar_lrint
-  init: xnn_init_qs8_conv_minmax_fp32_scalar_lrint_params
+- name: xnn_qs8_igemm_minmax_fp32_ukernel_2x2__scalar_lrintf
+  init: xnn_init_qs8_conv_minmax_fp32_scalar_lrintf_params
   k-block: 1
-- name: xnn_qs8_igemm_minmax_fp32_ukernel_3x2__scalar_lrint
-  init: xnn_init_qs8_conv_minmax_fp32_scalar_lrint_params
+- name: xnn_qs8_igemm_minmax_fp32_ukernel_3x2__scalar_lrintf
+  init: xnn_init_qs8_conv_minmax_fp32_scalar_lrintf_params
   k-block: 1
-- name: xnn_qs8_igemm_minmax_fp32_ukernel_4x2__scalar_lrint
-  init: xnn_init_qs8_conv_minmax_fp32_scalar_lrint_params
+- name: xnn_qs8_igemm_minmax_fp32_ukernel_4x2__scalar_lrintf
+  init: xnn_init_qs8_conv_minmax_fp32_scalar_lrintf_params
   k-block: 1
-- name: xnn_qs8_igemm_minmax_fp32_ukernel_1x4__scalar_lrint
-  init: xnn_init_qs8_conv_minmax_fp32_scalar_lrint_params
+- name: xnn_qs8_igemm_minmax_fp32_ukernel_1x4__scalar_lrintf
+  init: xnn_init_qs8_conv_minmax_fp32_scalar_lrintf_params
   k-block: 1
-- name: xnn_qs8_igemm_minmax_fp32_ukernel_2x4__scalar_lrint
-  init: xnn_init_qs8_conv_minmax_fp32_scalar_lrint_params
+- name: xnn_qs8_igemm_minmax_fp32_ukernel_2x4__scalar_lrintf
+  init: xnn_init_qs8_conv_minmax_fp32_scalar_lrintf_params
   k-block: 1
-- name: xnn_qs8_igemm_minmax_fp32_ukernel_3x4__scalar_lrint
-  init: xnn_init_qs8_conv_minmax_fp32_scalar_lrint_params
+- name: xnn_qs8_igemm_minmax_fp32_ukernel_3x4__scalar_lrintf
+  init: xnn_init_qs8_conv_minmax_fp32_scalar_lrintf_params
   k-block: 1
-- name: xnn_qs8_igemm_minmax_fp32_ukernel_4x4__scalar_lrint
-  init: xnn_init_qs8_conv_minmax_fp32_scalar_lrint_params
+- name: xnn_qs8_igemm_minmax_fp32_ukernel_4x4__scalar_lrintf
+  init: xnn_init_qs8_conv_minmax_fp32_scalar_lrintf_params
   k-block: 1
-- name: xnn_qs8_igemm_minmax_fp32_ukernel_1x2__scalar_magic
-  init: xnn_init_qs8_conv_minmax_fp32_scalar_magic_params
+- name: xnn_qs8_igemm_minmax_fp32_ukernel_1x2__scalar_fmagic
+  init: xnn_init_qs8_conv_minmax_fp32_scalar_fmagic_params
   k-block: 1
-- name: xnn_qs8_igemm_minmax_fp32_ukernel_2x2__scalar_magic
-  init: xnn_init_qs8_conv_minmax_fp32_scalar_magic_params
+- name: xnn_qs8_igemm_minmax_fp32_ukernel_2x2__scalar_fmagic
+  init: xnn_init_qs8_conv_minmax_fp32_scalar_fmagic_params
   k-block: 1
-- name: xnn_qs8_igemm_minmax_fp32_ukernel_3x2__scalar_magic
-  init: xnn_init_qs8_conv_minmax_fp32_scalar_magic_params
+- name: xnn_qs8_igemm_minmax_fp32_ukernel_3x2__scalar_fmagic
+  init: xnn_init_qs8_conv_minmax_fp32_scalar_fmagic_params
   k-block: 1
-- name: xnn_qs8_igemm_minmax_fp32_ukernel_4x2__scalar_magic
-  init: xnn_init_qs8_conv_minmax_fp32_scalar_magic_params
+- name: xnn_qs8_igemm_minmax_fp32_ukernel_4x2__scalar_fmagic
+  init: xnn_init_qs8_conv_minmax_fp32_scalar_fmagic_params
   k-block: 1
-- name: xnn_qs8_igemm_minmax_fp32_ukernel_1x4__scalar_magic
-  init: xnn_init_qs8_conv_minmax_fp32_scalar_magic_params
+- name: xnn_qs8_igemm_minmax_fp32_ukernel_1x4__scalar_fmagic
+  init: xnn_init_qs8_conv_minmax_fp32_scalar_fmagic_params
   k-block: 1
-- name: xnn_qs8_igemm_minmax_fp32_ukernel_2x4__scalar_magic
-  init: xnn_init_qs8_conv_minmax_fp32_scalar_magic_params
+- name: xnn_qs8_igemm_minmax_fp32_ukernel_2x4__scalar_fmagic
+  init: xnn_init_qs8_conv_minmax_fp32_scalar_fmagic_params
   k-block: 1
-- name: xnn_qs8_igemm_minmax_fp32_ukernel_3x4__scalar_magic
-  init: xnn_init_qs8_conv_minmax_fp32_scalar_magic_params
+- name: xnn_qs8_igemm_minmax_fp32_ukernel_3x4__scalar_fmagic
+  init: xnn_init_qs8_conv_minmax_fp32_scalar_fmagic_params
   k-block: 1
-- name: xnn_qs8_igemm_minmax_fp32_ukernel_4x4__scalar_magic
-  init: xnn_init_qs8_conv_minmax_fp32_scalar_magic_params
+- name: xnn_qs8_igemm_minmax_fp32_ukernel_4x4__scalar_fmagic
+  init: xnn_init_qs8_conv_minmax_fp32_scalar_fmagic_params
   k-block: 1