Add ProtocolUnit log preservation to compute services and object store, with reference in state store; expose via AlchemiscaleClient

[dotsdl]

It's currently the case that ProtocolUnits for many Protocols emit logs using the standard gufe logging mechanism, using their own ProtocolUnit.logger handler. However, within alchemiscale we neither capture nor preserve these logs in execution.

We should empower alchemiscale users to examine the logs emitted by a Task's ProtocolDAGResults by allowing them to retrieve the logs via:

• AlchemiscaleClient.get_result_logs(pdrr: ScopedKey, order='unit') : get logs for all ProtocolUnitResults in the ProtocolDAGResult, ordered by 'time' or by 'unit'
• AlchemiscaleClient.get_unit_logs(purr: ScopedKey) : get the logs for a single ProtocolUnitResult
• AlchemiscaleClient.get_result_units(pdrr: ScopedKey) : get ScopedKeys for all ProtocolUnitResultRefs given the ScopedKey of their ProtocolDAGResultRef

This will require that our compute services capture logs from each ProtocolUnit they execute, then upload those logs to the object store alongside the ProtocolDAGResult itself, creating a ProtocolUnitResultRef and a ProtocolUnitResultLogRef in the state store to enable retrieval. The ProtocolUnitResultRef for each ProtocolUnitResult in the ProtocolDAGResult will need to preserve dependency relationships to the other ProtocolUnitResultRefs in order to enable dependency-order reporting. The same ProtocolUnitResultRefs would likely be used for STDERR, STDOUT, and result file retrieval implemented under a similar pattern later.

Dependent somewhat on #348, since we assume ProtocolDAGResultRef ScopedKeys are now exposed to users.