Summary:
Adds `common/ValueGuesser.ts` with logic for guessing column type and widget options (only for dates/datetimes) from an array of strings, and converting the strings to the guessed type in a lossless manner, so that converting back to Text gives the original values.
Changes `_ensure_column_accepts_data` in Python to call an exported JS method using the new logic where possible.
Test Plan: Added `test/common/ValueGuesser.ts` to unit test the core guessing logic and a DocApi end-to-end test for what happens to new columns.
Reviewers: georgegevoian
Reviewed By: georgegevoian
Differential Revision: https://phab.getgrist.com/D3290
