[v-next] Rename globalArgument and namedParameters

[alcuadrado]

When discussing the help messages with @zoeyTM, we found that the wording was a bit confusing, so we decided to rename "global arguments" to "global options", and "named parameters" to "task options".

Basically, --option vs positional parameter, depending on whether the argument is passed with -- or positionally.

We should rename these concepts in the codebase to be consistent.