Read setting values from <PLUGIN_NAME>_<SETTING_NAME> env var, taking precedence over <PLUGIN_NAMESPACE>_<SETTING_NAME>
As suggested in #2208 (comment 388529270):
At that point, the distinction between
env_aliasesis lost, and we could always prefer to read and write from
envas just another alias.
To connect this with the "at which point we would not need the
namespaceat all anymore, and can instead just use the underscorized
namedirectly" conclusion above, we could always prefer the
<PLUGIN_NAME>_<SETTING_NAME>env var for reading and writing, and treat all of
env_aliasesas aliases. That, we could even implement today without having to untangle the whole
namespacemess, although that's obviously something we should do at some point as well.