Exclude more lines from test coverage (#1663)

These fall into a few categories:
- `_unreachable()`
- Verbose print messages
- Errors that should never practically occur (alloc/read/write failure,
  more than UINT32_MAX anonymous labels, etc)

src/gfx/pal_sorting.cpp

@@ -40,7 +40,7 @@ void sortIndexed(
 					return true;
 				}
 			}
-			unreachable_(); // This should not be possible
+			unreachable_(); // LCOV_EXCL_LINE
 		});
 	}
 }