Make Data.List.Inits fast

Fixes #9345. Use a modified banker's queue to achieve amortized optimal
performance for inits. The previous implementation was extremely slow.

Reviewed By: nomeata, ekmett, austin

Differential Revision: https://phabricator.haskell.org/D329

(cherry picked from cde3a77f9703966145cae481ee35f52dcca2cf7d)