Add metrics to `TxStatusManager` service (#2868)

Closes https://github.com/FuelLabs/fuel-core/issues/2851

## Description
This PR adds the following metrics to the `TxStatusManager` service:
* The total number of prunable statuses currently stored in the tx
status manager
* The total number of non-prunable statuses currently stored in the tx
status manager
* The number of entries currently stored in the pruning queue
* The age of the oldest transaction in the pruning queue

### Before requesting review
- [X] I have reviewed the code myself

### After merging, notify other teams

- [X] [Rust SDK](https://github.com/FuelLabs/fuels-rs/)
- [X] [Platform
documentation](https://github.com/FuelLabs/devrel-requests/issues/new?assignees=&labels=new+request&projects=&template=NEW-REQUEST.yml&title=%5BRequest%5D%3A+)
(for out-of-organization contributors, the person merging the PR will do
this)

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Co-authored-by: Green Baneling <XgreenX9999@gmail.com>