[mojo-stdlib] Replace `register_passable` `__init__ -> Self` usages in `stdlib/src/memory`

[MertCelik]

Replaces register_passable __init__ -> Self usages in stdlib/src/memory. 3 of 6 PRs for https://github.com/modularml/mojo/issues/2037

• [x] Replace /builtin #2075
• [x] Replace /collections #2089
• [x] Replace /memory #2090
• [ ] Replace /os
• [ ] Replace /utils
• [ ] Replace misc