skytools v3.9.1

Fixes:

• sqltools: mark exists_* functions as returning bool
• basetypes: sync DictRow with Mapping
• basetypes: describe additional psycopg2 api

Cleanups:

• build: create abi3 wheels
• ci: drop unmaintained create-release, upload-release-asset actions
• ci: build aarch64 wheel
• ci: test on pypy