feat: add probing policy

[kkafar]

Description

This PR extends probing mechanisms in GA and solutions introduced here should also be taken into consideration when implementing / extending logging mechanisms for other algorithms.

• Added ProbingPolicy trait
• Added GenerationInterval probing policy
• Added ElapsedTime probing policy
• Added new PolicyDrivenProbe - this probe can be passed a ProbingPolicy and it will log only when given policy allows it to
• Changed the way probing are exported out of crate::ga::probe module - now they are exported directly, not via their designated module. That means old import:

use ecrs::ga::probe::stdout_probe::StdoutProbe

now becomes

use ecrs::ga::probe::StdoutProbe

• Added Aggregated probe, which can be passed a vector of probes and executes them sequentially.
• Minor refactors of codebase to make aforementioned changes possible.

Linked issues

Resolves #171
Resolves #170