Release v1.12.0

Job Failure Threshold (#265)

* add class for managing failure threshold

* make cancellation token source protected

* Update Cognite.Common/FailureThresholdManager.cs

Co-authored-by: Einar <einar@omang.com>

* convert token source to property

* switch to custom callback action

* return failed jobs on callback

* skip creating hashset of dictionary keys

* add tests

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Co-authored-by: Einar <einar@omang.com>