Memory usage fixes for Haddock

- Do not include `mi_globals` in the `NoBackend` backend. It was only included
  for Haddock, but Haddock does not actually need it. This causes a 200MB
  reduction in max residency when generating haddocks on the Agda codebase
  (roughly 1GB to 800MB).

- Make haddock_{parser,renamer}_perf tests more accurate by forcing docs to
  be written to interface files using `-fwrite-interface`

Bumps haddock submodule.

Metric Decrease:
    haddock.base