Require Julia 1.10 and deprecate type-pirating methods

Compat dropped support for Julia versions prior to v1.6 about 14 months after it was released, 6 months after it became LTS (by the release of 1.7). As v1.10 has been released about 13 months ago and became LTS about 5 months ago, we can start thinking about dropping support for versions prior to v1.10. Which this PR does. Seizing the opportunity of a major version bump, this does another change that might be worth more discussion: It resolves #814 by applying it to the few remaining offenders. Maybe this PR - threatening to actually have an impact - receives more feedback than #814... If there are objections, I happily remove the last two commits to reduce this to the minimum-required-version-bump only.