Fix window_scatter_max/min crash on f64 tensors

[blasphemetheus]

window_scatter_max and window_scatter_min crash with f64 tensors.

  t = Nx.iota({6}, type: :f64)                                                          
  s = Nx.iota({3}, type: :f64)                                                          
  init = Nx.tensor(0.0, type: :f64)                                                     
  Nx.window_scatter_max(t, s, init, {2}, strides: [2], padding: :valid)                 
  # ** (ArgumentError) unexpected size for tensor data, expected 384 bits got: 288 bits

This does not affect f32. The scatter result in select_and_scatter wasn't cast to the output type before to_binary, causing a binary size mismatch for f64 (8-byte) tensors.

So the fix is: value |> Nx.as_type(output_type) |> to_binary()

running window_scatter_f64_test.exs on main

     Nx.WindowScatterF64Test [test/nx/window_scatter_f64_test.exs]                      
       * test window_scatter_max still works with f32 [L#22]                            
       * test window_scatter_max still works with f32 (3.1ms) [L#22]                    
       * test window_scatter_max works with f64 [L#4]                                   
       * test window_scatter_max works with f64 (1.5ms) [L#4]                           
                                                                                        
       1) test window_scatter_max works with f64 (Nx.WindowScatterF64Test)              
          test/nx/window_scatter_f64_test.exs:4                                         
          ** (ArgumentError) unexpected size for tensor data, expected 384 bits got: 288
      bits                                                                              
          code: result = Nx.window_scatter_max(t, s, init, {2}, strides: [2], padding:  
     :valid)                                                                            
          stacktrace:                                                                   
            (nx 0.11.0) lib/nx/binary_backend.ex:118: Nx.BinaryBackend.from_binary/2    
            (nx 0.11.0) lib/nx.ex:7486: Nx.window_scatter_max/5                         
            test/nx/window_scatter_f64_test.exs:8: (test)                               
                                                                                        
       * test window_scatter_min works with f64 [L#13]                                  
       * test window_scatter_min works with f64 (0.08ms) [L#13]                         
                                                                                        
       2) test window_scatter_min works with f64 (Nx.WindowScatterF64Test)              
          test/nx/window_scatter_f64_test.exs:13                                        
          ** (ArgumentError) unexpected size for tensor data, expected 384 bits got: 288
      bits                                                                              
          code: result = Nx.window_scatter_min(t, s, init, {2}, strides: [2], padding:  
     :valid)                                                                            
          stacktrace:                                                                   
            (nx 0.11.0) lib/nx/binary_backend.ex:118: Nx.BinaryBackend.from_binary/2    
            (nx 0.11.0) lib/nx.ex:7648: Nx.window_scatter_min/5                         
            test/nx/window_scatter_f64_test.exs:17: (test)                              
                                                                                        
                                                                                        
     Finished in 0.01 seconds (0.01s async, 0.00s sync)                                 
     3 tests, 2 failures 

originally part of the closed fuzz test edge case PR #1707

[polvalente]

This should be a regular test if we're only fixing a binary backend bug

[polvalente]

Just saw we have the tests, so let's remove this one