Faucet: repurpose cap and slice args to apply to single IPs (#16381)

* Single use stmt

* Log request IP

* Switch cap and slice to apply per IP

* Use SOL in logs, error msgs

* Use thiserror instead of overloading io::Error

* Return memo transaction for requests that exceed per-request-cap

* Handle faucet memos in cli

* Add some docs, esp about memo transaction

* Use SOL symbol & standardize memo

Co-authored-by: Michael Vines <mvines@gmail.com>

* Differentiate faucet tx-length errors

* Populate signature in cli airdrop memo case

Co-authored-by: Michael Vines <mvines@gmail.com>

cli/tests/vote.rs

@@ -35,7 +35,6 @@ fn test_vote_authorize_and_withdraw() {
         &faucet_addr,
         &config.signers[0].pubkey(),
         100_000,
-        &config,
     )
     .unwrap();