Repot all templates into a single directory (paritytech#3460)

The first step towards
paritytech#3155

Brings all templates under the following structure

```
templates
|   parachain
|   |   polkadot-launch
|   |   runtime              --> parachain-template-runtime
|   |   pallets              --> pallet-parachain-template
|   |   node                 --> parachain-template-node
|   minimal
|   |   runtime              --> minimal-template-runtime
|   |   pallets              --> pallet-minimal-template
|   |   node                 --> minimal-template-node
|   solochain
|   |   runtime              --> solochain-template-runtime
|   |   pallets              --> pallet-template (the naming is not consistent here)
|   |   node                 --> solochain-template-node
```

The only note-worthy changes in this PR are: 

- More `Cargo.toml` fields are forwarded to use the one from the
workspace.
- parachain template now has weights and benchmarks
- adds a shell pallet to the minimal template
- remove a few unused deps 


A list of possible follow-ups: 

- [ ] Unify READMEs, create a parent README for all
- [ ] remove references to `docs.substrate.io` in templates
- [ ] make all templates use `#[derive_impl]`
- [ ] update and unify all licenses
- [ ] Remove polkadot launch, use
https://github.com/paritytech/polkadot-sdk/blob/35349df993ea2e7c4769914ef5d199e787b23d4c/cumulus/zombienet/examples/small_network.toml
instead.