feat(bigquery): non-nullable schema support for embedded fields in struct

[ssabdb]

Bigquery supports embedded non-nullable checks inside bigquery schemas, allowing any non-nullable fields in the schema to persist down into bigquery.

Description of changes

Override _from_ibis_Struct for bigquery to allow the adding of a non-nullable field constraint

Issues closed

Resolves #10188, at least for bigquery. There might be opportunities to implement this change in other backends as well.

[cpcloud]

BigQuery tests look good:

…/ibis on  ssabdb/main:main is 📦 v9.5.0 via 🐍 v3.12.5 via ❄️   impure (ibis-3.12.5-env)
❯ pytest -m bigquery -n auto --dist loadgroup --snapshot-update -q
bringing up nodes...
..................sssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssss...sssssssssssssssssssss.....x................s........x............................x.............xx...x.....x...x..xxxx..xx.xxxxx...xx..x.xx.xxxx..x.x.xxxxx..x.xxxxxx.xx.xxxxxxxxxx.xxxxx.xxxxxxxx..xx.xxxxxxxxxx.xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx.xx.x.xx.xxxxxxxxxxxxxxxxxxxxx [ 17%]
xxxxxxxxx..xxxxxx...x.x.x.......x......x.......xx.....x...............x............x.......x.....................................................x.............x............x...............x......x...x......xxx.....xx.........x......x...x....xxx..X.x....X..x..x.x.x.....x...x....X..x...xx.x.....xxx.xx........xX.x.x.xx.............x.xxx......x........x.x....x...x........x.xxx.x..x..x.xx..x [ 35%]
..x.....x...xx...x......x....x.................................x........................x............................x.............................................................x..x....x...........x........xxx...x...................x......x.....................x........xx..x.....x.......x..x....x...x....x.....................................x.......x........x................x.......x. [ 52%]
..............x..................x..................x..xx...x.....x...xxx........xx........x.........x.x.x..xx...............x...........x..........................xxxxx...xxx.xxx...x.....x...x..xx.x.....x.........s...x.........xs.....x......s.....x.................................x...........x.......x...xx.....xx.x.....x..x......x........xx..x.x.x.....x....xxx.x.....xx..........xx.x... [ 70%]
......xxx...........x...xxx.......x...xx.................................xx.......x.............x.......x......x.x......x.......x...Xs.x......s.xsx.xs.................................................................................................................................................................................x............................................................. [ 88%]
...........x..............s..........s....s...........x..........................................................x.....x..................................................................................................................s...............x..........                                                                                                                                 [100%]
1719 passed, 132 skipped, 350 xfailed, 5 xpassed in 362.04s (0:06:02)

[cpcloud]

Thanks for the PR!

[ssabdb]

Thanks for the fast merge!