Update `expressions` format default

[texodus]

This PR fixes an omnibus of issues with this release's refactoring of the expressions config.

• Updates all tests, examples and docs to use new format.
• Fixes lots of formatting issues not enforced by the linter (especially in the html! macro).
• Adds log warnings when the legacy expressions format is detected.
• Fixes Python to have the same behavior.defaults as JavaScript.
• Fixes CI Python script to not install perspective-python from pypi.