metal : refactor + optimize (#15857)

* metal : refactor

ggml-ci

* cont : refactor FA-vec kernel

* cont : print metal library load time

* minor : warn to debug + bettern kernel names

ggml-ci

* metal : optimize mul_mv q8_0

ggml-ci

* metal : simplify FA pipeline creation functions

ggml-ci

* metal : improve naming consistency

* metal : safer function constants offsets

ggml-ci

* metal : comments

ggml-ci

ggml/src/ggml-metal/ggml-metal-impl.h

@@ -20,8 +20,8 @@
 #define N_R0_Q5_1 4
 #define N_SG_Q5_1 2
 
-#define N_R0_Q8_0 4
-#define N_SG_Q8_0 2
+#define N_R0_Q8_0 2
+#define N_SG_Q8_0 4
 
 #define N_R0_MXFP4 2
 #define N_SG_MXFP4 2
@@ -68,6 +68,11 @@
 #define N_R0_IQ4_XS 2
 #define N_SG_IQ4_XS 2
 
+// function constants offsets
+#define FC_FLASH_ATTN_EXT              100
+#define FC_FLASH_ATTN_EXT_VEC          200
+#define FC_FLASH_ATTN_EXT_VEC_REDUCE   300
+
 // kernel argument structs
 //
 // - element counters (e.g. ne00) typically use int32_t to reduce register usage
@@ -236,9 +241,11 @@ typedef struct {
     int32_t  ne11;
     int32_t  ne_12_2; // assume K and V are same shape
     int32_t  ne_12_3;
+    int32_t  ns10;
     uint64_t nb11;
     uint64_t nb12;
     uint64_t nb13;
+    int32_t  ns20;
     uint64_t nb21;
     uint64_t nb22;
     uint64_t nb23;
@@ -258,10 +265,43 @@ typedef struct {
     float    logit_softcap;
 } ggml_metal_kargs_flash_attn_ext;
 
+typedef struct {
+    int32_t  ne01;
+    int32_t  ne02;
+    int32_t  ne03;
+    uint64_t nb01;
+    uint64_t nb02;
+    uint64_t nb03;
+    int32_t  ne11;
+    int32_t  ne_12_2; // assume K and V are same shape
+    int32_t  ne_12_3;
+    int32_t  ns10;
+    uint64_t nb11;
+    uint64_t nb12;
+    uint64_t nb13;
+    int32_t  ns20;
+    uint64_t nb21;
+    uint64_t nb22;
+    uint64_t nb23;
+    int32_t  ne32;
+    int32_t  ne33;
+    uint64_t nb31;
+    uint64_t nb32;
+    uint64_t nb33;
+    int32_t  ne1;
+    int32_t  ne2;
+    int32_t  ne3;
+    float    scale;
+    float    max_bias;
+    float    m0;
+    float    m1;
+    int32_t  n_head_log2;
+    float    logit_softcap;
+} ggml_metal_kargs_flash_attn_ext_vec;
+
 typedef struct {
     int32_t  nrows;
-    int32_t  ne20;
-} ggml_metal_kargs_flash_attn_ext_reduce;
+} ggml_metal_kargs_flash_attn_ext_vec_reduce;
 
 typedef struct {
     int32_t  ne00;