b9535e09

By: Tom Sydney Kerckhove <syd@cs-syd.eu>

Mutation phase: take a MutationRunSettings record, not positional args

runMutationMode took six positional arguments including two adjacent
Bools (failFast, emitRedundancy) that could be swapped with no type
error.  Replace them with a named MutationRunSettings record so each
field is set by name at the call sites (runDriver, runDiff, the test).
Pure refactor; behaviour unchanged.

Suite timing

Time to Start Worker time Duration Time to finish Idle
Config - - - - 13m07s
Eval - - - - -
Build - - - - -
Suite - - - - 13m07s