Prefer spilling in window fullGroupBuffered when there was at least one spill

[sopel39]

When spill happened, prefer spilling rather than merging with memory.
This prevents query node-level OOM when query is spill heavy

Additionally, a minor bug was fixed in spoilable hash aggregation, when removable memory
was not covered to user memory when merge with memory happens

Additional context and related issues

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## General
* Reduce out-of-memory errors in window queries when spill is enabled. ({issue}`issuenumber`)

Fixes #10596

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