Add Task indicators, methods for getting these in AlchemiscaleClient, for introspection of Task history and running state

[dotsdl]

Currently, users have very limited ability to understand the current state/behavior of an incomplete Task. In order to help users to assess problematic Tasks, the following indicators on a Task would be useful:

• how many times a Task has been claimed
• how long Task has been in current status (datetime of last status change)
• what compute service registration, if any, last claimed it
• what compute service registration, if any, is currently claiming it

We would also like to add hostname to compute service registration generation, which could help compute operators track down problematic cases compute-side.

The above indicators should be exposed in some useful way to users via the AlchemiscaleClient.