[mlir][bufferization] Improve analysis for element-wise operations

Before this change, two equivalent operands that bufferize to a memory read and write, respectively, were always conflicting. This change improves the analysis for ops that bufferize to element-wise access. Such ops can bufferize in-place, because an original element value is not needed anymore after computing and writing an updated element value.

This change allows ops such as the following one to bufferize in-place:
```
  %0 = linalg.elemwise_binary {fun = #linalg.binary_fn<add>}
      ins(%a, %b : tensor<5xf32>, tensor<5xf32>)
      outs(%a : tensor<5xf32>) -> tensor<5xf32>
```

Differential Revision: https://reviews.llvm.org/D156887