These are some fixes that can be implemented for the wallet_* examples in the example-crates dir.

• Print balances either in BTC or sats (but not both)
• wallet_esplora_async appears to be printing the KeychainKind twice, and forgets to print spk0
• Use tempfile instead of std::env::tempdir, as this should automatically clean up temporary files
• Consider changing wallet examples to use signet and possibly a different server URL to fix rate limiting issues
• Try to recycle the sats so that running an example doesn't result in a net loss of "funds"