Make all arg bindings have flag BaseTypeArg.
Make all arg bindings have flag BaseTypeArg.

It's unclear what the prupose of the previous restriction to Local only was.
And we need it to be set for all arg bindings so that immutable.Set does not
fail with a variance error.

sjrd/dotty,densh/dotty,lampepfl/dotty,dotty-staging/dotty,dotty-staging/dotty,sjrd/dotty,som-snytt/dotty,lampepfl/dotty,densh/dotty,som-snytt/dotty,som-snytt/dotty,som-snytt/dotty,sjrd/dotty,dotty-staging/dotty,sjrd/dotty,dotty-staging/dotty,lampepfl/dotty,sjrd/dotty,dotty-staging/dotty,lampepfl/dotty,som-snytt/dotty,lampepfl/dotty