Add a script to get subscribed and onboarded laconicd accounts (#22)

Part of [laconicd testnet validator enrollment](#19)

The script:
- Fetches onboarded participants using the configured laconicd GQL endpoint
- Reads a given CSV file with subscribers data
- Fetches all the onboarding txs using given laconicd RPC endpoint
- For each subscriber registered as a participant, maps the laconic pubkey and latest onboarding tx height
- Outputs the result in a CSV

Co-authored-by: Nabarun <nabarun@deepstacksoft.com>
Reviewed-on: #22
Co-authored-by: Prathamesh Musale <prathamesh.musale0@gmail.com>
Co-committed-by: Prathamesh Musale <prathamesh.musale0@gmail.com>

This commit was merged in pull request #24.