.NET Core 3.1 - retarget integrations libs plus adapter compat

[garypretty]

• Retarget integration libraries to target .NET Core 3.1
• Admends to adapters to ensure async operations used (sync operations blocked by default in .NET Core 3+)

[coveralls]

Pull Request Test Coverage Report for Build 102268

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 10 unchanged lines in 8 files lost coverage.
• Overall coverage increased (+1.4%) to 79.613%

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Files with Coverage Reduction	New Missed Lines	%
/libraries/Microsoft.Bot.Builder.Dialogs/ObjectPath.cs	1	86.46%
/libraries/Microsoft.Bot.Builder.Dialogs/Prompts/OAuthPrompt.cs	1	56.4%
/libraries/Microsoft.Bot.Builder/Inspection/InspectionMiddleware.cs	1	78.89%
/libraries/Microsoft.Bot.Expressions/BuiltInFunctions.cs	1	93.12%
/libraries/Microsoft.Bot.Expressions/LRUCache.cs	1	82.93%
/libraries/Microsoft.Bot.Expressions/TriggerTrees/Trigger.cs	1	85.09%
/libraries/Microsoft.Bot.Builder.Azure/CosmosDbStorageOptions.cs	2	75.0%
/libraries/Microsoft.Bot.Builder/MemoryTranscriptStore.cs	2	86.09%

Totals
Change from base Build 102132:	1.4%
Covered Lines:	10809
Relevant Lines:	13577

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💛 - Coveralls

[fuselabs]

✔️ No Binary Compatibility issues for Microsoft.Bot.Builder.dll compared against version 4.6.3
✔️ No Binary Compatibility issues for Microsoft.Bot.Builder.AI.Luis.dll compared against version 4.6.3
✔️ No Binary Compatibility issues for Microsoft.Bot.Builder.AI.QnA.dll compared against version 4.6.3
✔️ No Binary Compatibility issues for Microsoft.Bot.Builder.ApplicationInsights.dll compared against version 4.6.3
✔️ No Binary Compatibility issues for Microsoft.Bot.Builder.Azure.dll compared against version 4.6.3
✔️ No Binary Compatibility issues for Microsoft.Bot.Builder.Dialogs.dll compared against version 4.6.3
✔️ No Binary Compatibility issues for Microsoft.Bot.Builder.Integration.ApplicationInsights.Core.dll compared against version 4.6.3
✔️ No Binary Compatibility issues for Microsoft.Bot.Builder.Integration.AspNet.Core.dll compared against version 4.6.3
✔️ No Binary Compatibility issues for Microsoft.Bot.Builder.TemplateManager.dll compared against version 4.6.3
✔️ No Binary Compatibility issues for Microsoft.Bot.Builder.Testing.dll compared against version 4.6.3
✔️ No Binary Compatibility issues for Microsoft.Bot.Configuration.dll compared against version 4.6.3
✔️ No Binary Compatibility issues for Microsoft.Bot.Connector.dll compared against version 4.6.3
✔️ No Binary Compatibility issues for Microsoft.Bot.Schema.dll compared against version 4.6.3
✔️ No Binary Compatibility issues for Microsoft.Bot.Streaming.dll compared against version 4.6.3