HPCC-31895 Fix deserialization and merging of nested stats

[shamser]

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[github-actions]

Jira Issue: https://hpccsystems.atlassian.net//browse/HPCC-31895

Jirabot Action Result:
Workflow Transition: Merge Pending
Updated PR

[shamser]

All stats deserialized by the thor manager from workers should be set rather than merged. I found that the nested stats were being merged rather than set, causing multiple counting of nested stats. The PR fixes this issue.

Note that the local execute time for nested functions in a parallel project will be longer than the execute time for parent activity/subgraph. This is because each thread in the parallel project would be making a call to the nested function and the nested function’s execute time will be the sum of the execute time for all the threads. (The local project does have a stat NumParallel that may be used to determine if the larger execute time for nested functions is reasonable.)

[ghalliday]

Please can you target to 9.4.x
That is where the original (misplaced) fix was: https://github.com/hpcc-systems/HPCC-Platform/pull/18428/files

[ghalliday]

Did you rebase onto an out of date 9.4.x?

Line 2733 is currently

ensureNested().deserialize(in);

and needs to change back to deserializeMerge.