Memory usage is too high for large tenant

**AzGovViz version**
6.7.2

**CodeRunPlatform**
Jenkins, on AKS, with azure-powershell runner image, version: '15.0.0-alpine-3.22'.
limitMemory:'12Gi', requestMemory:'3Gi', limitCpu:'2.5'

**Describe the bug**
Script memory usage is growing continuously, without important memory release, and finish by a OOMKilled, because it is using all the memory.

Despite a aggressive garbage collection settings.

First memory ramp end with "CustomDataCollection Subscriptions processing" end (16:59).
A secund memory ramp end after "processing (pre) TenantSummary RoleAssignments" (17:17).

**Screenshots**

**Additional context**

Command line :
pwsh/AzGovVizParallel.ps1 -ManagementGroupId 'myMainMG' -OutputPath 'AzGovViz-Output' -HierarchyMapOnly -NoPIMEligibility -ShowMemoryUsage -LargeTenant -DoTranscript -CriticalMemoryUsage 70

Environment vars :
DOTNET_GCHeapHardLimitPercent=0x63
DOTNET_GCHeapCount=4

Landing zone insights :
- 54 relevant Management Groups
- 115 relevant Subscriptions
- RoleAssignments (all 39558)