Use stdlib logging if structlog is missing #319

Job	Run time
Verify dev env (ubuntu-latest)	13s
Build & verify package	45s
Verify dev env (windows-latest)	1m 33s
Type-check package	28s
Build docs & run doctests	26s
Tests on 3.8	21s
Type-check API on 3.8	20s
Tests on 3.9	26s
Type-check API on 3.9	26s
Tests on 3.10	30s
Type-check API on 3.10	24s
Tests on 3.11	19s
Type-check API on 3.11	16s
Tests on 3.12	38s
Type-check API on 3.12	30s
Combine & check coverage.	12s
Ensure everything required is passing for branch protection.	3s
	7m 50s

Provide feedback