tests: Big push to get the tests to pass again. - Lots of fixes everywhere in the code. - Try to handle debug logging in the multiprocessing worker pool when running in pytest. Not perfect, but usable for now. - Replace all `.md` test files with `.html` since now a auto-format extension always sets the format. - Replace `out` with `outfiles` in most places since now blog archives are added to the bake output and I don't want to add expected outputs for blog archives everywhere.

---
config:
    site:
        root: /~john/public/
in:
    pages/about.html: 'URL: {{page.url}}, LINK: {{pcurl("missing")}}'
    pages/_index.html: 'URL: {{page.url}}'
outfiles:
    about.html: 'URL: /%7Ejohn/public/about.html, LINK: /%7Ejohn/public/missing.html'
    index.html: 'URL: /%7Ejohn/public/'