✨ add latches (locks) to items in the bufferpool to make them read only during use

[joocer]

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We currently materialize items we read from the buffer pool to byte arrays so that if the item is removed or moved which in use, we're working on a copy of the data. this materialization is costly.

It may be more efficient to latch the items (either explicitly with an unlatch and/or with a timeout) so we can keep the memoryview and flip a bit rather than materialize to ensure the data isn't updated during use.