Fixing subtyping of refined types
Fixing subtyping of refined types

Refined type subtyping needs to take into account all information
that was seen about members of both refined types. This is handled by
storing context info in `pendingRefinedBases` and making use of this
to selective rebase qualifiers when comparing refined types.

Note: This commit fails in pos/collections and dotc/ast, presumably because
of bad interaction between the refined subtyping and the "matchingNames" logic
(which will go away).

auvik/dotty,sjrd/dotty,som-snytt/dotty,lampepfl/dotty,VladimirNik/dotty,dotty-staging/dotty,sjrd/dotty,lampepfl/dotty,som-snytt/dotty,sjrd/dotty,lampepfl/dotty,spetz911/dotty,lampepfl/dotty,dotty-staging/dotty,vsalvis/dotty,reactormonk/dotty,som-snytt/dotty,angi2/dotty,AlexSikia/dotty,svalaskevicius/dotty,densh/dotty,lampepfl/dotty,som-snytt/dotty,yusuke2255/dotty,reactormonk/dotty,sjrd/dotty,dotty-staging/dotty,AlexSikia/dotty,vsalvis/dotty,folone/dotty,spetz911/dotty,yusuke2255/dotty,svalaskevicius/dotty,auvik/dotty,densh/dotty,folone/dotty,sjrd/dotty,VladimirNik/dotty,dotty-staging/dotty,angi2/dotty,som-snytt/dotty,dotty-staging/dotty