fix(snowflake): ensure that timestamp conversion from parquet files is correct

[cpcloud]

Fixes a bug where the scale was incorrectly left up to Snowflake, which can produce incorrectly scaled values if a timestamp is read in as a variant integer and then cast to string.

[cpcloud]

Oh, it looks like they may have actually fixed this upstream using a new parquet format parameter USE_LOGICAL_TYPE (https://community.snowflake.com/s/article/How-to-load-logical-type-TIMESTAMP-data-from-Parquet-files-into-Snowflake).

[cpcloud]

Snowflake is all green:

…/ibis on  fix-snowflake-parquet-timestamps is 📦 v9.0.0 via 🐍 v3.12.2 via ❄️   impure (ibis-3.12.2-env)
❯ pytest -m snowflake -n auto --dist loadgroup -q
bringing up nodes...
....x....x.............x..............................x...........xx...x.....x..............x......x........x......................x.xx.....x.................x........................xx..... [ 11%]
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..x........x..x....x.....xx.........x..........x....x..............xx..........x..x............s..................x.............s.....................................s................x...... [ 44%]
x.............x...x........s..........................................................x.......x........x..............x....................xx..............xx...xx......x.......x............. [ 55%]
.x.........xx..x.x......x..x.x.x.....x....x.............xx.x.xx.....x..x..x..xxx..x.xx..xx.xx.xx.xx.xxx..x...x.x.x.xxxx..x..xx..x.xx.xxx..xxxxx.x.x.x.x..xx.xxxxxxxxx..x..x.xxxx..x...xx.x..x. [ 67%]
x..xx.xxxx.x..........xxx................x.....................................x..x.....x....................x.......x.....................x...x......x...x.....x.........x.x....xx...x.xx.xx.. [ 78%]
xx..x..xx...xx..x..........x.x.........x......x...x.....x.x..........x...xxx.x.x.x...xx....x.x....x...s.....x.....x...............x.........................xx.........xx..................... [ 89%]
.......x...........................................................................................................s.......................s......s..............................              [100%]
1458 passed, 9 skipped, 231 xfailed in 116.53s (0:01:56)

[gforsyth]