Merging same-object - multiple versions from different pools would not always result in correct ordering.
When merging keep inputs separate.
```
λ mc ls --versions local/testbucket
------ before ------
[2024-03-05 20:17:19 CET] 228B STANDARD 1f163718-9bc5-4b01-bff7-5d8cf09caf10 v3 PUT hosts
[2024-03-05 20:19:56 CET] 19KiB STANDARD null v2 PUT hosts
[2024-03-05 20:17:15 CET] 228B STANDARD 73c9f651-f023-4566-b012-cc537fdb7ce2 v1 PUT hosts
------ after ------
λ mc ls --versions local/testbucket
[2024-03-05 20:19:56 CET] 19KiB STANDARD null v3 PUT hosts
[2024-03-05 20:17:19 CET] 228B STANDARD 1f163718-9bc5-4b01-bff7-5d8cf09caf10 v2 PUT hosts
[2024-03-05 20:17:15 CET] 228B STANDARD 73c9f651-f023-4566-b012-cc537fdb7ce2 v1 PUT hosts
```
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