extend_params fix after n_particles removed

[andrewdipper]

Fix examples after change to extend_params in blackjax-devs/blackjax#694.

Additionally in the TemperedSMC example max_num_doublings was changed to 6 instead of the default 10 since we regularly hit max_num_doublings due to the small step size (I believe this is for illustrative purposes). On a gpu device the example is extraordinarily slow without the change - and still takes ~2 mins with it. It seems far too slow but I haven't been able to find any explanation.

For reference:

CPU (10000 samples, max_num_doublings=10):
step_size = 1e-2:
HMC: 50 steps / 1.14s
NUTS: 30 steps / .964s

step_size = 1e-3
HMC: 50 / 1.14s
NUTS: 273 / 1.9s

step_size = 1e-4
HMC: 50 / 1.18s
NUTS: 926 / 4.23s

GPU (1000 samples - 10x fewer samples..., max_num_doublings=10):
step_size = 1e-2:
HMC: 50 / 3.31s
NUTS: 30 / 7.3s

step_size = 1e-3:
HMC: 50 / 3.32s
NUTS: 267 / 63s

step_size = 1e-4
HMC: 50 / 3.31s
NUTS: 926.4 / 237s