ADFS DKM Master Key Export

'Identifies an export of the ADFS DKM Master Key from Active Directory. References: https://blogs.microsoft.com/on-the-issues/2020/12/13/customers-protect-nation-state-cyberattacks/, https://www.fireeye.com/blog/threat-research/2020/12/evasive-attacker-leverages-solarwinds-supply-chain-compromises-with-sunburst-backdoor.html?1 To understand further the details behind this detection, please review the details in the original PR and subequent PR update to this: https://github.com/Azure/Azure-Sentinel/pull/1562#issue-551542469 https://github.com/Azure/Azure-Sentinel/pull/1512#issue-543053339 '