Fix LRU dropping memos too early

[Veykril]

Fixes #669

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[codspeed-hq]

CodSpeed Performance Report

Merging #673 will not alter performance

_{Comparing Veykril:veykril/push-zovznokvrpqs (b5882c9) with master (ae416f1)}

Summary

✅ 9 untouched benchmarks

[MichaReiser]

Huh, there's a LRU test failure now

[Veykril]

Ahaha, well the test checks for how many entries are alive via global counter that is decreased on drop. But now we no longer drop them eagerly. So the test is actually wrong in that regard. (my other PR also had to change that)

[Veykril]

Actually not quite, it was trying to trigger a new revision by creating an input but nowadays that actually doesn't trigger one (only setting an input does)