Optimize divisions and remainders by constants. #5167
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As well as the IR version to 1.20-SNAPSHOT.
This allows to better mutualize their implementation with the signed divisions. Moreoever, our 3 implementation strategies (JS with `RuntimeLong`, JS with `bigint` and Wasm) have different efficient implementations of those operations. Using IR BinaryOps for them allows each backend to use the most appropriate implementation, while letting the optimizer generically manipulate their mathematical properties.
Now that we have the tools to perform the division by multiplication and shift, we can do it with the hard-coded `Strategy`. This also allows to remove the hackish way of reusing `unsignedDivModHelper` to compute `toString()`.
Previously, we had various places in the linker that special-cased division by non-zero constants to consider them pure. Now that the optimizer systematically rewrites all such divisions into multiplications and shifts, these special-cases are effectively dead code, so we can remove them.
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Needs more tests and benchmarks.
Also more references to sources, such as relevant papers.