Added DRep delegation injections to Conway

[Soupstraw]

Description

resolves #3995

Checklist

• Commit sequence broadly makes sense and commits have useful messages
• New tests are added if needed and existing tests are updated
• When applicable, versions are updated in .cabal and CHANGELOG.md files according to the
  versioning process.
• The version bounds in .cabal files for all affected packages are updated. If you change the bounds in a cabal file, that package itself must have a version increase. (See RELEASING.md)
• All visible changes are prepended to the latest section of a CHANGELOG.md for the affected packages. New section is never added with the code changes. (See RELEASING.md)
• Code is formatted with fourmolu (use scripts/fourmolize.sh)
• Cabal files are formatted (use scripts/cabal-format.sh)
• hie.yaml has been updated (use scripts/gen-hie.sh)
• Self-reviewed the diff

[lehins]

Unfortunately implementation for injection still has the same problem of requiring to load the whole input into memory, because it has to pass over the source ListMap twice.

I made a suggestion that should help you fix that.

[lehins]

One more important issue and I think it is good to go.

[lehins]

Beautiful!