refactor(hub-contracts): [ETH-896] Move to network-contracts subpackage (#1028)

Moved Hub contracts from `hub-contracts` subpackage to
`network-contracts` subpackage and removed the `hub-contracts`
subpackage.

## Other changes

- Removed obsolete `preparebuild` script

## Future improvements

- Move all test contracts to `test-contracts` (now it contains only Hub
test contracts, including `ERC20Mintable` used also by `NodeRegistry`)
- Maybe could use `Wallet` directly, instead of `hardhatEthers.Wallet`
in hub tests?

Author: teogeb

package-lock.json

@@ -8,7 +8,6 @@
   "workspaces": [
     "./packages/config",
     "./packages/network-contracts",
-    "./packages/hub-contracts",
     "./packages/network-subgraphs",
     "./packages/ens-sync-script",
     "./packages/dev-chain-fast"

package.json

@@ -2,7 +2,7 @@ FROM node:18-slim
 RUN apt-get update && apt-get install curl -y
 WORKDIR /usr/src/hardhat
 COPY ./dist ./package.json ./*.tgz ./hardhat.config.js ./start.sh ./
-RUN npm i --omit=dev ./streamr-network-contracts-*.tgz ./streamr-hub-contracts-*.tgz
+RUN npm i --omit=dev ./streamr-network-contracts-*.tgz
 
 CMD ["/bin/bash", "/usr/src/hardhat/start.sh"]
 # ENTRYPOINT [ "/bin/bash" ]