Introduce chain-spec-generator and document Weight Generation process (polkadot-fellows#127)

Closes polkadot-fellows#50

- Adds the `chain-spec-generator` from
polkadot-fellows#78 and
polkadot-fellows#81, updated to work
with `master`.
- Adds detailed instructions to the `README.md` for generating weights
for fellowship runtimes

I am currently generating weights and will add them in a seperate PR
when they are ready.

TODO
- [x] Add step for checking weight outputs using
https://github.com/ggwpez/substrate-weight-compare in readme
- [ ] Fix encointer chain spec defaults, or open new issue for it

### Why not use the `polkadot-sdk` generic chain-spec-builder?

The genesis state configs generated by this CLI are unusable for
benchmarking, due to poor defaults. We need better defaults for our
pallet genesis state before we can use this CLI. See also
paritytech/polkadot-sdk#2713.

---------

Co-authored-by: Bastian Köcher <[email protected]>
Co-authored-by: Javier Viola <[email protected]>
Co-authored-by: NachoPal <[email protected]>
Co-authored-by: Svyatoslav Nikolsky <[email protected]>
Co-authored-by: Branislav Kontur <[email protected]>
Co-authored-by: Oliver Tale-Yazdi <[email protected]>
Co-authored-by: Bastian Köcher <[email protected]>

Author: 7 people

CHANGELOG.md

@@ -7,6 +7,8 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 ## [Unreleased]
 
 ### Added
+
+- Introduce chain spec generator ([polkadot-fellows/runtimes#127](https://github.com/polkadot-fellows/runtimes/pull/127))
 - Add [Encointer](https://encointer.org) system parachain runtime, completing [RFC22](https://github.com/polkadot-fellows/RFCs/blob/main/text/0022-adopt-encointer-runtime.md) ([polkadot-fellows/runtimes#80](https://github.com/polkadot-fellows/runtimes/pull/80))
 
 ## [1.1.0] 10.01.2024