[eng/common] Helper function "Install-ModuleIfNotInstalled" is not threadsafe

[mikeharder]

In pipeline "Autorest Regen Preview", the following command fails intermittently. I think this might be a race condition, where multiple parallel threads (39 and 40) are installing the same module at the same time, and it's possible for one thread to see a partial install.

   1:7>Project "/mnt/vss/_work/1/s/azure-sdk-for-net/eng/service.proj" (1:7) is building "/mnt/vss/_work/1/s/azure-sdk-for-net/sdk/healthinsights/Azure.Health.Insights.ClinicalMatching/src/Azure.Health.Insights.ClinicalMatching.csproj" (40:9) on node 2 (GenerateCode target(s)).
    40>_GenerateCodeForTypeSpec:
         pwsh -NoProfile -NonInteractive -executionpolicy Unrestricted -File /mnt/vss/_work/1/s/azure-sdk-for-net/sdk/healthinsights/Azure.Health.Insights.ClinicalMatching/src/../../../../eng/common/scripts/TypeSpec-Project-Sync.ps1 /mnt/vss/_work/1/s/azure-sdk-for-net/sdk/healthinsights/Azure.Health.Insights.ClinicalMatching/src/.. 
    39>_GenerateCodeForTypeSpec:
         Installing module powershell-yaml with min version 0.4.1 from https://www.powershellgallery.com/api/v2
    40>_GenerateCodeForTypeSpec:
         Installing module powershell-yaml with min version 0.4.1 from https://www.powershellgallery.com/api/v2
         Using module powershell-yaml with version 0.4.7.
    39>_GenerateCodeForTypeSpec:
         Using module powershell-yaml with version 0.4.7.
    40>_GenerateCodeForTypeSpec:
         ParentContainsErrorRecordException: /home/cloudtest/.local/share/powershell/Modules/powershell-yaml/0.4.7/Load-Assemblies.ps1:28
         Line |
           28 |  …           return [Reflection.Assembly]::LoadFrom($assemblies["core"])
              |                     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
              | Exception calling "LoadFrom" with "1" argument(s): "Could not load file
              | or assembly
              | '/home/cloudtest/.local/share/powershell/Modules/powershell-yaml/0.4.7/lib/netstandard2.1/YamlDotNet.dll'. The system cannot find the file specified. "

https://dev.azure.com/azure-sdk/internal/_build/results?buildId=2906603&view=logs&j=a59e8b2b-145b-5c08-bac3-c8d41476a686&t=b360b5d6-342a-59db-d57c-25f0340a37f5&l=4073

I suspect the root cause is one of the Install-ModuleIfNotInstalled commands in azure-sdk-for-net:

https://github.com/search?q=repo%3AAzure%2Fazure-sdk-for-net%20powershell-yaml&type=code

One level deeper, I believe the root cause is using Install-Module -Force, which can overwrite the module and cause a parallel Import-Module to fail.

https://github.com/Azure/azure-sdk-for-net/blob/3ab9a7ac57f8a7672079c1ffba1ad8f95cfa5a1b/eng/common/scripts/Helpers/PSModule-Helpers.ps1#L86