Streamline CU::RepositoryRegistry.setup-repositories
Streamline CU::RepositoryRegistry.setup-repositories

- part 1
- avoid multiple lookups for the same key
- replace "ab{$foo}bar" by "ab" ~ $foo ~ "bar"
  The "ab{$foo}bar" construct should be avoided, especially if the
  variable is a native, as it causes an actual Callable to be created,
  which then gets called, and then coerced to a Str.  Whereas the
  "ab" ~ $foo ~ "bar" construct basically codegens to nqp::concat()s.

rakudo/rakudo,rakudo/rakudo,labster/rakudo,tony-o/rakudo,tony-o/rakudo,tbrowder/rakudo,softmoth/rakudo,softmoth/rakudo,MasterDuke17/rakudo,tbrowder/rakudo,tbrowder/rakudo,nbrown/rakudo,MasterDuke17/rakudo,MasterDuke17/rakudo,rakudo/rakudo,MasterDuke17/rakudo,nbrown/rakudo,nbrown/rakudo,tony-o/rakudo,tbrowder/rakudo,tbrowder/rakudo,rakudo/rakudo,nbrown/rakudo,tony-o/rakudo,salortiz/rakudo,nbrown/rakudo,tbrowder/rakudo,nbrown/rakudo,salortiz/rakudo,labster/rakudo,tony-o/rakudo,labster/rakudo,MasterDuke17/rakudo,salortiz/rakudo,softmoth/rakudo,rakudo/rakudo,salortiz/rakudo,rakudo/rakudo,softmoth/rakudo,salortiz/rakudo,labster/rakudo,tony-o/rakudo,MasterDuke17/rakudo,softmoth/rakudo,labster/rakudo,salortiz/rakudo,labster/rakudo