Add injection-recoveries

[ThibeauWouters]

It would be great to have more support for handling injection-recoveries which can be used to assess the validity of the surrogates and check for any potential biases. A small but incomplete list of action items:

• Injection-recoveries for GRB models
• Handling the amount of fake (non-)detections to be processed
• Make the time grid on which the (non-)detections are placed more flexible and realistic.
• Make the magnitude errors vary randomly or in certain prescribed manners
• Allow user-defined settings to propagate accordingly, such as detection limits.

In inference/injection.py there is a rough setup/script that can be extended with the above points.

[ThibeauWouters]

In #9, there has been some progress.