Optimize the functions called in circuit_launch_by_extend_info()

Ref to https://trac.torproject.org/projects/tor/ticket/8902#comment:10

You can see that on a loaded HS, some functions are called quite a lot and they take a lot of CPU.

https://people.torproject.org/~dgoulet/tor-hs-perf-100-circ.png

They should be optimize to bring that CPU usage down.

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information