HPCC-32111 Use compression in global merge activity

[jakesmith]

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Testing:

[jakesmith]

@ghalliday - please review. Questionable whether should be 9.8 vs master.

[github-actions]

Jira Issue: https://hpccsystems.atlassian.net//browse/HPCC-32111

Jirabot Action Result:
Workflow Transition To: Merge Pending
Updated PR

[ghalliday]

@jakesmith 1 minor question.

[ghalliday]

rwFlags |= spillCompInfo;

for consistency with elsewhere? Really this should be a single piece of common code.... but that can be a separate refactoring. The same logic seems to be done two different ways.

[jakesmith]

Yes, I meant to have it like that, now fixed.
Have opened separate JIRA to common code like this: https://hpccsystems.atlassian.net/browse/HPCC-32881

[jakesmith]

@ghalliday - uninitialized issue fixed/squashed in.

[github-actions]

Jirabot Action Result:
Added fix version: 9.8.36
Workflow Transition: 'Resolve issue'