(This release merges the v0.19.2, which was not properly released)

• Package simplego:
  • Fixed Gather of scalar values.
  • Fixed Where checking of shape.
  • New ops: NotEqual, Erf, ArgMinMax, ReduceWindow, ReduceBitwise{And,Or,Xor} and
    ReduceLogical{And,Or,Xor}
  • Fixed initialization of re-used buffers where needed.
• Package backends/default:
  • Only include XLA by default on linux/amd64 platforms.
• Package shapeinference:
  • Changed to return errors instead of exceptions.
• Package types/tensors:
  • Removed dependency to gopjrt/pjrt -- otherwise we'll always need to install the C/C++ library.
• Package types/shape:
  • Added Shape.Iter() and Shape.IterOn().
• Package backend:
  • Backend interface now returns errors instead of panicking.
• Package graph:
  • Added NewExecOrError and Exec.CallOrError as error-returning alternatives.
• gofmt cleanups by @zjtv