Add common pattern fusion

[HobbitQia]

Fuse gep + load/store, mul + add in FusePatternPass which I observed them in most kernels and provide a C++ test case to verify the correctness.

For now, the fusion should be written manually, I am working on searching on common patterns based on frequency and fusing different pattern into the same op but with different attributes to differentiate each other. I will finish this these days.

[tancheng]

fusing different pattern into the same op but with different attributes to differentiate each other.

This sounds a good idea, which is different from creating every neura.new_op for each fused op. However, we then need to carefully put sufficient/many attributes to "differentiate each other". Anyways, the design about those attributes can be first prototyped in a simple way and then improved gradually.

[tancheng]

Looks like the merge main into main deletes all code changes? my bad, sth wrong with my github