[mlir][tosa] Constant folding for reciprocal

[mlir][tosa] Constant folding for reciprocal

Add constant fold for tosa.reciprocal, which can be applied if the input is a dense constant tensor. The reciprocal is computed for every element and the result is a tensor with the same dimensions as the input tensor.

As the input tensor might require a lot of memory and the folding might double the required memory, a heuristic decides when to actually apply the folding. Currently, the operation will be replaced only if the input constant is a splat (i.e. requires little memory) or has in single user (similar to the already existing fold for constant transposes). This keeps the additionally required space low.

Differential Revision: https://reviews.llvm.org/D150578