New migrations system, ported from sqlite-migrate

[simonw]

Refs:

• Migrations system: sqlite_utils.Migrations and sqlite-utils migrate command, ported from sqlite-migrate #752

---

📚 Documentation preview 📚: https://sqlite-utils--754.org.readthedocs.build/en/754/

[codecov]

Codecov Report

❌ Patch coverage is 96.66667% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 95.26%. Comparing base (8f0c06e) to head (3423195).

Files with missing lines	Patch %	Lines
sqlite_utils/cli.py	95.65%	4 Missing ⚠️
sqlite_utils/migrations.py	98.21%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #754      +/-   ##
==========================================
+ Coverage   95.16%   95.26%   +0.10%     
==========================================
  Files           8        9       +1     
  Lines        3122     3255     +133     
==========================================
+ Hits         2971     3101     +130     
- Misses        151      154       +3     

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.