Adds number_of_packets property to the packet collection

[andrewfullard]

:pencil: Description

Type: :rocket: feature

Fixes #2738 by adding the number to the packet collection. Better option than in the transport state.

:vertical_traffic_light: Testing

How did you test these changes?

• [x] Testing pipeline
• [ ] Other method (describe)
• [ ] My changes can't be tested (explain why)

:ballot_box_with_check: Checklist

• [x] I requested two reviewers for this pull request
• [ ] I updated the documentation according to my changes
• [ ] I built the documentation by applying the build_docs label

Note: If you are not allowed to perform any of these actions, ping (@) a contributor.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 66.66667% with 1 line in your changes missing coverage. Please review.

Project coverage is 69.12%. Comparing base (38a35c3) to head (46c7d0f). Report is 8 commits behind head on master.

Files	Patch %	Lines
tardis/transport/montecarlo/packet_collections.py	66.66%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #2740 +/- ## =========================================== + Coverage 36.58% 69.12% +32.54% =========================================== Files 186 188 +2 Lines 14859 14946 +87 =========================================== + Hits 5436 10332 +4896 + Misses 9423 4614 -4809 ```

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[wkerzendorf]

Is this sensible? Should this not be a property?

[andrewfullard]

Is this sensible? Should this not be a property?

I don't know if jitclasses can use the @property decorator. I'll look into it.

[tardis-bot]

*beep* *bop* Hi human, I ran ruff on the latest commit (46c7d0fdbcce21c7d2977a130042f90e16eee384). Here are the outputs produced. Results can also be downloaded as artifacts here. Summarised output:

```diff ```

Complete output(might be large):

```diff ```