TIMESTAMP math causes compilation error

[Micah Wylde]

create table nexmark with (
    connector = 'nexmark',
    event_rate = '5'
);

select bid.datetime - DATE '2023-12-03'
from nexmark
group by 1;

error[E0277]: cannot subtract `SystemTime` from `SystemTime`
   --> pipeline/src/main.rs:126:54
    |
126 | ...                   left - std::time::UNIX_EPOCH
    |                            ^ no implementation for `SystemTime - SystemTime`
    |
    = help: the trait `Sub` is not implemented for `SystemTime`
    = help: the following other types implement trait `Sub<Rhs>`:
              <SystemTime as Sub<time::date_time::DateTime<time::date_time::offset_kind::Fixed>>>
              <SystemTime as Sub<time::duration::Duration>>
              <SystemTime as Sub<time::offset_date_time::OffsetDateTime>>
              <SystemTime as Sub<std::time::Duration>>

[Micah Wylde]

Fixed in #441