Address performance regression in GQL subscriptions when using productBlockInstances

[Mark90]

The new SubscriptionModel querying from 3.2.0 turns out to have some adverse effects on the performance of the subscriptions GQL query, specifically when using the productBlockInstances field. This particularly affects the SubscriptionDropdownOptions query.

This PR mitigates this partially by:

• Only loading the "extended" domain model if productBlockInstances { ... } contains field inUseByRelations
• Adding a ModelCacheExtension to reuse loaded subscription models throughout each GQL query operation

Which, at least for the SubscriptionDropdownOptions query, reduces the execution time by 2/3rd.

Bumps version to 3.2.2

---

Related orchestrator-ui-library PR: workfloworchestrator/orchestrator-ui-library#1872

[codspeed-hq]

CodSpeed Performance Report

Merging #922 will not alter performance

_{Comparing gql-subscriptions-performance (0d5689f) with main (b584705)}

Summary

✅ 13 untouched benchmarks

[codecov]

Codecov Report

Attention: Patch coverage is 85.18519% with 4 lines in your changes missing coverage. Please review.

Project coverage is 83.49%. Comparing base (b584705) to head (0d5689f).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
orchestrator/services/subscriptions.py	33.33%	2 Missing ⚠️
orchestrator/utils/get_subscription_dict.py	60.00%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #922      +/-   ##
==========================================
- Coverage   83.49%   83.49%   -0.01%     
==========================================
  Files         204      205       +1     
  Lines       10186    10206      +20     
  Branches     1020     1022       +2     
==========================================
+ Hits         8505     8521      +16     
- Misses       1411     1414       +3     
- Partials      270      271       +1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[Mark90]

Internal issue https://git.ia.surfsara.nl/netdev/automation/projects/orchestrator/-/issues/2288