Everywhere: Rename ASSERT => VERIFY

(...and ASSERT_NOT_REACHED => VERIFY_NOT_REACHED)

Since all of these checks are done in release builds as well,
let's rename them to VERIFY to prevent confusion, as everyone is
used to assertions being compiled out in release.

We can introduce a new ASSERT macro that is specifically for debug
checks, but I'm doing this wholesale conversion first since we've
accumulated thousands of these already, and it's not immediately
obvious which ones are suitable for ASSERT.

Userland/Libraries/LibGfx/PNGLoader.cpp

@@ -387,7 +387,7 @@ NEVER_INLINE FLATTEN static bool unfilter(PNGLoadingContext& context)
                 }
             }
         } else {
-            ASSERT_NOT_REACHED();
+            VERIFY_NOT_REACHED();
         }
         break;
     case 4:
@@ -396,7 +396,7 @@ NEVER_INLINE FLATTEN static bool unfilter(PNGLoadingContext& context)
         } else if (context.bit_depth == 16) {
             unpack_grayscale_with_alpha<u16>(context);
         } else {
-            ASSERT_NOT_REACHED();
+            VERIFY_NOT_REACHED();
         }
         break;
     case 2:
@@ -405,7 +405,7 @@ NEVER_INLINE FLATTEN static bool unfilter(PNGLoadingContext& context)
         } else if (context.bit_depth == 16) {
             unpack_triplets_without_alpha<u16>(context);
         } else {
-            ASSERT_NOT_REACHED();
+            VERIFY_NOT_REACHED();
         }
         break;
     case 6:
@@ -425,7 +425,7 @@ NEVER_INLINE FLATTEN static bool unfilter(PNGLoadingContext& context)
                 }
             }
         } else {
-            ASSERT_NOT_REACHED();
+            VERIFY_NOT_REACHED();
         }
         break;
     case 3:
@@ -468,11 +468,11 @@ NEVER_INLINE FLATTEN static bool unfilter(PNGLoadingContext& context)
                 }
             }
         } else {
-            ASSERT_NOT_REACHED();
+            VERIFY_NOT_REACHED();
         }
         break;
     default:
-        ASSERT_NOT_REACHED();
+        VERIFY_NOT_REACHED();
         break;
     }
 
@@ -658,7 +658,7 @@ static int adam7_height(PNGLoadingContext& context, int pass)
     case 7:
         return context.height / 2;
     default:
-        ASSERT_NOT_REACHED();
+        VERIFY_NOT_REACHED();
     }
 }
 
@@ -680,7 +680,7 @@ static int adam7_width(PNGLoadingContext& context, int pass)
     case 7:
         return context.width;
     default:
-        ASSERT_NOT_REACHED();
+        VERIFY_NOT_REACHED();
     }
 }
 
@@ -809,7 +809,7 @@ static bool decode_png_bitmap(PNGLoadingContext& context)
             return false;
         break;
     default:
-        ASSERT_NOT_REACHED();
+        VERIFY_NOT_REACHED();
     }
 
     munmap(context.decompression_buffer, context.decompression_buffer_size);
@@ -1026,7 +1026,7 @@ RefPtr<Gfx::Bitmap> PNGImageDecoderPlugin::bitmap()
             return nullptr;
     }
 
-    ASSERT(m_context->bitmap);
+    VERIFY(m_context->bitmap);
     return m_context->bitmap;
 }