Create DocumentLoader.LoadAll method

[bryanrcarlson]

There is redundant code to load documents into Cosmos in Pipelines. This should be part of the DocumentLoader class.

Example of code:

int docsLoaded = 0;
int docsError = 0;
foreach(SoilSample sample in transformed)
{
  ResourceResponse<Document> result = 
    await loader.LoadNoReplace(sample);
  if(result.StatusCode == HttpStatusCode.Created)
  {
    etlEvent.Outputs.Add(result.Resource.Id);
    docsLoaded++;
  }
  else { docsError++; }

    // Notify data written then sleep to conserve Cosmos RU
    Console.Write(".");
    Thread.Sleep(40);
  }

Function should take "Thread.Sleep" as argument
Function should return a list of successes (or a string?) and list of errors. Possibly a tuple. This info needs to be logged in an EtlEvent:

etlEvent.Logs.Add(
  $"Loaded {docsLoaded.ToString()} SoilSamples");
etlEvent.Logs.Add(
  $"Error loading {docsError.ToString()} SoilSamples");