refactor: Remove `devtoolsInProd` option, default to dev/prod

[rschristian]

Breaking change, don't merge before we're ready!

devtoolsInProd feels a bit unnecessary, as we can instead toggle based on dev/prod environment (as can the user). If a user wanted to always enable devtools, no problem, they can pass a constant true into the plugin options like so: preact({ devToolsEnabled: true })