Diagnostics: Add RetryAfter value

[j82w]

The current cosmos diagnostics does not log the RetryAfter time. This makes it difficult to determine if the SDK is honoring the RetryAfter value and/or if the RetryAfter value is high which is the cause of the SDK delay.

The header value:

azure-cosmos-dotnet-v3/Microsoft.Azure.Cosmos/src/Headers/Headers.cs

Line 150 in 5e4b98a

internal virtual string RetryAfterLiteral

This should be added to the StoreResult like BELatency so the v2 SDK will also get the value in the diagnostics:
https://msdata.visualstudio.com/_git/CosmosDB?path=/Product/Microsoft.Azure.Documents/SharedFiles/StoreResult.cs&version=GBmaster&line=340&lineEnd=341&lineStartColumn=1&lineEndColumn=1&lineStyle=plain&_a=contents

[j82w]

#2818