QNN: re-export a16w8 with MinMaxObserver activations

The previous files used make_quantizer's MovingAverageMinMaxObserver default,
whose moving average trails the real activation range. Measured on an S26 Ultra
over 500 ImageNetV2 images: 70.00% top-1 before, 71.80% after, against 72.20%
for fp32. Quantization loss drops from 2.20 points to 0.40 at the same size.

Only the v81 file is device-validated; the other four are the same code path and
calibration compiled for Hexagon versions we have no hardware for.

qnn/config.json

@@ -34,7 +34,9 @@
             }
           ]
         }
-      }
+      },
+      "quantized": true,
+      "default": false
     },
     {
       "file": "efficientnet_v2_s_qnn_a16w8_v73.pte",
@@ -62,7 +64,9 @@
             }
           ]
         }
-      }
+      },
+      "quantized": true,
+      "default": false
     },
     {
       "file": "efficientnet_v2_s_qnn_a16w8_v75.pte",
@@ -90,7 +94,9 @@
             }
           ]
         }
-      }
+      },
+      "quantized": true,
+      "default": false
     },
     {
       "file": "efficientnet_v2_s_qnn_a16w8_v79.pte",
@@ -118,7 +124,9 @@
             }
           ]
         }
-      }
+      },
+      "quantized": true,
+      "default": false
     },
     {
       "file": "efficientnet_v2_s_qnn_a16w8_v81.pte",
@@ -146,7 +154,9 @@
             }
           ]
         }
-      }
+      },
+      "quantized": true,
+      "default": true
     }
   ]
 }

qnn/efficientnet_v2_s_qnn_a16w8_v69.pte

@@ -1,3 +1,3 @@
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 size 32839168

qnn/efficientnet_v2_s_qnn_a16w8_v73.pte

@@ -1,3 +1,3 @@
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 size 25556480

qnn/efficientnet_v2_s_qnn_a16w8_v75.pte

@@ -1,3 +1,3 @@
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-size 25556480
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+size 25552384

qnn/efficientnet_v2_s_qnn_a16w8_v79.pte

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-size 25646592
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+size 25642496

qnn/efficientnet_v2_s_qnn_a16w8_v81.pte

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 size 25712128