feat: Adding Rockset db engine spec

[srinify]

Adds db_engine_spec for Rockset (https://rockset.com/)

[villebro]

Awesome, I look forward to testing this! LGTM, one minor comment. Also, if you're in the mood for adding unit tests for some of those Rockset funct (eopch_to_dttm, epocu_ms_to_dttm, convert_dttm etc), it will help protect us against regressions.

[codecov]

Codecov Report

Merging #16167 (1ae627c) into master (ccfc95f) will decrease coverage by 0.12%.
The diff coverage is 71.61%.

❗ Current head 1ae627c differs from pull request most recent head b567aa6. Consider uploading reports for the commit b567aa6 to get more accurate results

@@            Coverage Diff             @@
##           master   #16167      +/-   ##
==========================================
- Coverage   76.73%   76.61%   -0.13%     
==========================================
  Files         996      998       +2     
  Lines       52999    53228     +229     
  Branches     6738     6764      +26     
==========================================
+ Hits        40668    40778     +110     
- Misses      12102    12220     +118     
- Partials      229      230       +1     

Flag	Coverage Δ
hive	?
mysql	81.54% <76.81%> (-0.07%)	⬇️
postgres	81.57% <76.81%> (-0.07%)	⬇️
presto	81.40% <76.81%> (-0.02%)	⬇️
python	81.83% <76.81%> (-0.32%)	⬇️
sqlite	81.21% <76.81%> (-0.07%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
superset-frontend/src/components/Form/Form.tsx	100.00% <ø> (ø)
...ontrols/DndColumnSelectControl/DndColumnSelect.tsx	46.42% <ø> (-0.94%)	⬇️
...rontend/src/explore/components/optionRenderers.tsx	100.00% <ø> (ø)
...perset-frontend/src/views/CRUD/chart/ChartList.tsx	72.61% <ø> (ø)
...set-frontend/src/views/CRUD/data/database/types.ts	100.00% <ø> (ø)
...set-frontend/src/views/CRUD/welcome/ChartTable.tsx	73.17% <0.00%> (-1.83%)	⬇️
...c/visualizations/TimeTable/TimeTableChartPlugin.js	75.00% <ø> (ø)
superset/common/query_object.py	90.66% <ø> (ø)
superset/datasets/commands/importers/v1/utils.py	58.97% <0.00%> (ø)
superset/examples/bart_lines.py	27.58% <0.00%> (ø)
... and 51 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update ccfc95f...b567aa6. Read the comment docs.