[Unity] Improve buffer allocation for handling duplicated buffer names.

[LeiWang1999]

Refer to this issue
#16433 , the relax Pass FuseTIR creates intermediate name by

n->name = param->name_hint + "_intermediate";

which may lead to some bugs when we encounter two fused blocks with the same param name, for example what I encountered in resnet-18, the conv+add+multiply+add, the fused two add operators' block may point to the same block.

So we should provide a method to get an unique name for each in duplicate buffers.

auto unify_name_hints = [this, &buffer, &param]() {
        String base_name = buffer->name;
        String unique_name = base_name + "_intermediate";
        size_t unique_id = 0;
        std::unordered_set<std::string> names;

        for (auto& _buffer : func_info_.alloc_buffers) {
          names.insert(_buffer->name);
        }

        while (names.find(unique_name) != names.end()) {
          unique_name = unique_name + "_" + std::to_string(++unique_id);
        }
 return unique_name;
 };

[LeiWang1999]

Please CC @Hzfengsy

[junrushao]

LGTM!