Added Managed Identity authentication

[asaharn]

Pull Request Description

managed identity authentication support

---

Breaking Changes:

• None

Features:

• Managed Identity authentication

Fixes:

• None

Examples: 1) If System-assigned Managed Identity( no need to pass KUSTO_MANAGED_CLIENT_ID):

df.write
  .format("com.microsoft.kusto.spark.datasource")
      .format("com.microsoft.kusto.spark.datasource")
      .option(KustoSinkOptions.KUSTO_CLUSTER, "MyCluster")
      .option(KustoSinkOptions.KUSTO_DATABASE, "MyDatabase")
      .option(KustoSinkOptions.KUSTO_TABLE, "MyTable")
      .option(KustoSinkOptions.KUSTO_MANAGED_IDENTITY_AUTH, true.toString)
      .mode(SaveMode.Append)
      .save()

2) User-assigned Managed identity:

df.write
  .format("com.microsoft.kusto.spark.datasource")
      .format("com.microsoft.kusto.spark.datasource")
      .option(KustoSinkOptions.KUSTO_CLUSTER, "MyCluster")
      .option(KustoSinkOptions.KUSTO_DATABASE, "MyDatabase")
      .option(KustoSinkOptions.KUSTO_TABLE, "MyTable")
      .option(KustoSinkOptions.KUSTO_MANAGED_IDENTITY_AUTH, true.toString)
      .option(KustoSinkOptions.KUSTO_MANAGED_CLIENT_ID, "xxxx-xxxx-xxxxx-xxxx")
      .mode(SaveMode.Append)
      .save()

[ag-ramachandran]

Hello @asaharn, couple of quick checks a) Documentation needs to be added b) Samples of MI tests can be added in the PR