Feat: Add queue history size metric

[chrisbeard]

Describe your changes
This adds a new queue metric that counts the number of GUIDs in that queue's history. This is useful for identifying excessive memory utilization from history and potential history garbage collection issues (where history grows faster than it's cleaned up).

Testing performed
[x] Unit test
[x] Integration test

Todo
[ ] Prometheus integration

[678098]

@chrisbeard do you want to try to extend the existing integration test with this new metric?

For this, you will have to do these things:

1. Extend JsonPrinter with the newly added metric here:
   

   blazingmq/src/groups/mqb/mqbstat/mqbstat_jsonprinter.cpp

   Line 121 in 698d7be

   populateMetric(&values, ctx, Stat::e_NO_SC_MSGS_ABS);

2. Update integration test JSON data in this file, this comment explains how:
   

   blazingmq/src/python/blazingmq/dev/it/data/data_metrics.py

   Line 22 in 698d7be

   Note: when the metrics collection evolves, it might be necessary to update

Alternatively I can do this

[chrisbeard]

@chrisbeard do you want to try to extend the existing integration test with this new metric?

For this, you will have to do these things:

1. Extend JsonPrinter with the newly added metric here:
   

   blazingmq/src/groups/mqb/mqbstat/mqbstat_jsonprinter.cpp

   Line 121 in 698d7be

   populateMetric(&values, ctx, Stat::e_NO_SC_MSGS_ABS);

2. Update integration test JSON data in this file, this comment explains how:
   

   blazingmq/src/python/blazingmq/dev/it/data/data_metrics.py

   Line 22 in 698d7be

   Note: when the metrics collection evolves, it might be necessary to update

Alternatively I can do this

I'll do it, should be easy.