[imp] Make the timer/scheduler to have precision alongside real-time speed

### Description
There are 2 types of timers:
- `realtime_timer`
- `step_timer`
Each one of them has its own role. What is required is kind of the combination of those two timers: a timer, which runs in real time but also has a bigger precision. This is achievable with the introduction of `fps` in the scheduler's loop. With that, the scheduler tick will be triggered with custom frequency, and with each tick, a dedicated amount of timesteps may be simulated.

### Expectation
It's possible to set real-time simulation speed and simulation accuracy.

Start by reading the existing realtime_timer and step_timer implementations, then trace the scheduler's loop and tick handling. Define how an fps setting controls scheduler ticks and how many timesteps each tick simulates. Done means real-time simulation speed and simulation accuracy can both be configured and work together.

Written by the indexing model from the issue text.