server: add hlint hints to replace case analysis with combinators

[abooij]

Description

This PR implements 8 new hlint hints that enforce usage of our onNothing and onLeft combinators. Thus it further improves on #6126. Example hints provided by these new hlint hints:

src-lib/Hasura/RQL/Types/Common.hs:(292,20)-(294,57): Warning: Use onNothing
Found:
  case x of
    Just v -> return v
    Nothing -> fail "integer passed is out of bounds"
Perhaps:
  onNothing x (fail "integer passed is out of bounds")

src-lib/Hasura/RQL/DDL/RemoteRelationship/Validate.hs:(434,7)-(436,25): Warning: Use onLeft
Found:
  case eitherScalar of
    Left _ -> throwError $ InvalidGraphQLName $ toSQLTxt scalarType
    Right s -> pure s
Perhaps:
  onLeft
    eitherScalar
    (\ _c -> throwError $ InvalidGraphQLName $ toSQLTxt scalarType)

These new hints are triggered 23 times on the current master codebase.

This PR also removes some dead code, namely coerceSet, from Hasura.Prelude.

Affected components

• Server
• Tests

[codingkarthik]

Not sure why this is removed from here. Is this change relevant to this PR?

[abooij]

No, it's not relevant. Would you rather see this change be merged separately?

[codingkarthik]

I guess it's just dead code removal. It's fine this way

[nicuveo]

We should check that Pro doesn't use it.

[abooij]

@nicuveo According to some quick greps, it's not used by pro.

[nicuveo]

Perfect, then. LGTM! :)

[codingkarthik]

LGTM

[tirumaraiselvan]

no cl required