fix(min-rate): set minimum rate to 1 bps

[Rubilmax]

Let's suppose the worst case scenario of a market not utilized for so long that the rate reached MIN_RATE_AT_TARGET and suddenly it is utilized 100%

So err = 1 because utilization = 100%

And we can calculate that: $r{t+1} = c \times min{rate} \times e^{adjSpeed \times elapsed}$

Which leads $elapsed = ln(\frac{r{t+1}}{c \times min{rate}}) \times \frac{1}{adjSpeed}$

Let's now plot $elapsed$ (in days) based on different values of $r_{t+1}$ and $c$:

$r_{t+1}$ \ $c$	1	1.5	2	4	5	6	8	10
0.01%	0	0	0	0	0	0	0	0
0.1%	16.8	13.9	11.8	6.7	5.1	3.7	1.6	0
1%	33.6	30.7	28.6	23.5	21.9	20.5	18.4	16.8
10%	50.4	47.5	45.4	40.3	38.7	37.3	35.2	33.6

[Rubilmax]

I'd like to note that I don't think we should think about absolute of rates, because I don't think we are able to tell how the market would react to a rate of 1 or 10bps, depending on assets & volume involved

So I think the most relevant thing is to think about order of magnitude changes in rates

It seems to me that under such extreme & illiquid market conditions, having to wait 10 days (with c = 1.5 or 2) before increasing the order of magnitude of the rate is a bit too much, so only taking this into account, I'd recommend c = 4 or even 6 (but it has other implications)

EDIT: oh! I just found out that 4 corresponds to the value used in tests!