`setLenUninit` missing for `--mm:orc`

[arnetheduck]

Nim Version

2.2.4

Description

#22767 added setLenUninit to ORC, but it's still missing from the gc - this creates an annoying imbalance with respect to newSeqUninit which is available for both, which makes porting code harder.

Current Output

Expected Output

Known Workarounds

No response

Additional Information

No response