Mainly the performance impact here comes from removing some unnecessary
checks and inlining `read_integer_fast()` directly into `op_column()`,
but I also added some fiddly nano-optimizations for fun
On main, we are roughly 3.4x slower than sqlite on `SELECT * FROM users
LIMIT 100`, and here we are roughly 3.2x slower, which ain't much, but
it's honest work.
A more impactful optimization, but a much more annoying refactor, would
be #2304Closes#2516
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