Implement DRep ratification with an 'always passing' threshold

[teodanciu]

Description

Closes #3612

An example of the computation:

For these Dreps:

D1 -> s1
D2 -> s2
D3 -> s3
D4 -> s4
Abstain -> sA
NoConfidence -> sN

and these votes:

D1 -> Yes
D2 -> No
D3 -> Abstain
D9 -> No  -- This is not in the drep distribution map

We need to compute this ratio in case of an action different from NoConfidence:
s1/(s1 + s2 + s3 + s4 + sA + sN - s3 -sA)
and this one for NoConfidence:
(s1 + sN)/(s1 + s2 + s3 + s4 + sA + sN - s3 -sA)

Because we don't have the ratios precomputed (as is the case for spo stake distribution), instead of folding to get the total and then subtracting the abstains, we fold the distribution and only add what's necessary, depending on the vote and on the action.

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

[Soupstraw]

Good work so far, could use some re-organizing before merge 👍

[teodanciu]

An example of the computation:

For these Dreps:

D1 -> s1
D2 -> s2
D3 -> s3
D4 -> s4
Abstain -> sA
NoConfidence -> sN

and these votes:

D1 -> Yes
D2 -> No
D3 -> Abstain
D9 -> No  -- This is not in the drep distribution map

We need to compute this ratio in case of an action different from NoConfidence:
s1/(s1 + s2 + s3 + s4 + sA + sN - s3 -sA)
and this one for NoConfidence:
(s1 + sN)/(s1 + s2 + s3 + s4 + sA + sN - s3 -sA)

Because we don't have the ratios precomputed (as is the case for spo stake distribution), instead of folding to get the total and then subtracting the abstains, we fold the distribution and only add what's necessary, depending on the vote and on the action.

[lehins]

Looks great! Thank you.

[teodanciu]

Good Haskell lessons from your review @lehins , thank you