Feature Request: Claim All Rewards

[jca-klk]

This is a follow-up on #348: Claim is working perfectly for a single hotspot 🎉

My use-case for helium-wallet-rs is to handle wallets with many (1000+) LoRaWAN hotspots.
The Helium mobile wallet app has a feature for "Claim All Rewards".

I could run my own loop to claim all rewards, but it looks like the wallet-app does some tricks with Solana blockhash I am not at ease with.
I also wonder if blockchain fees would be reduced in a "Claim All Rewards" transaction.

This issue is a feature request to add "claim all rewards" for all hotspots in a given wallet, on-par with the mobile wallet app.

Thank you!