Cardano Updates

Adding Milkomeda Open Oracle dev guide

3815: Cleanup nix setup: remove unused cabal shell r=Unisay a=Unisay

### Overview

This pull request cleans up our `flake.nix` configuration by

* removing the unused `cabal-shell.nix`
* making explicit which shell is created when doing `nix develop` (it's `….devShells.default`).

### Issue Number

ADP-2447

Co-authored-by: Yura Lazarev <[email protected]>

fix CI not running on bors branches

5023: fix CI not running on bors branches r=disassembler a=dermetfan

Looks like this was broken in #4930 as `prAndBorsIo` was added but not used.

Also removed `nix` from the task name. I do not see what purpose it has and it makes the names unnecessarily long. Also we happen to need the old names in #5018.

Co-authored-by: Robin Stumm <[email protected]>

I don't trust it. Compare these two runs:
1. https://github.com/input-output-hk/cardano-haskell-packages/actions/runs/4532746158/jobs/7984714895
2. https://github.com/input-output-hk/cardano-haskell-packages/actions/runs/4516172089/jobs/7954255360

The second is on the parent commit of the first, the commit itself is a
no-op, and yet the derivations
they build are not the same! Doing the same locally, I get a) a
different derivation, but b) the same derivation for both.

I conclude that what the CI is doing is questionable, the cache seems
like the most likely source of pollution.

I suspect whatever is causing this was also responsible for the no-op PR
spending a lot of time building tons of stuff.

* Update readme (cli flags, comment dsl, new format)

* Document the comment DSL

* Document CLI flags

* Mention new split rust/wasm output structure

* Remove unsupported section (to handle in issues instead as this tends
  to get very outdated)

* respond to comments + add supported.cddl

* minor fixes for comment placement in supported.cddl + remove unsupported optional fixed value from example