duplicate intermediate names generated that cause simpiler to fail

[TH3CHARLie]

A repro that fails on current main:

#include "Halide.h"
using namespace Halide;

int main() {
    Buffer<int> buf1, buf2;
    Func input("input");
    Func local_sum("local_sum");
    Func blurry("blurry");
    Var x("x"), y("y");
    input(x, y) = 2 * x + 5 * y;
    RDom r(-2, 5, -2, 5);
    local_sum(x, y) = 0;
    local_sum(x, y) += input(x + r.x, y + r.y);
    blurry(x, y) = cast<int32_t>(local_sum(x, y) / 25);
    {
        Pipeline p({blurry});
        std::map<std::string, Parameter> params;
        serialize_pipeline(p, "test.hlpipe", params);
        auto dp = deserialize_pipeline("test.hlpipe", params);
        buf1 = p.realize({128, 128});
    }
    {
        Var yo, yi, x_yo_f;
        input.vectorize(y).split(y, yo, yi, 2, TailStrategy::ShiftInwards).unroll(x).fuse(x, yo, x_yo_f);
        blurry.compute_root();
        input.compute_at(blurry, x);
        Pipeline p({blurry});
        buf2 = p.realize({128, 128});
    }
    return 0;
}

error:

Internal Error at /home/xuanda/dev/Serializer/Halide-clean/src/Simplify_Let.cpp:68 triggered by user code at : Condition failed: !var_info.contains(op->name): Simplify only works on code where every name is unique. Repeated name: input.s0.y.v3.base
[1]    387235 abort (core dumped)