wallet: add --url, remove --host/--rpc-host/--rpc-port/-rpc-tls (#4153)

Also by default the wallet now talks to testnet.solana.com instead of
localhost

scripts/wallet-sanity.sh

@@ -9,8 +9,8 @@ cd "$(dirname "$0")"/..
 # shellcheck source=multinode-demo/common.sh
 source multinode-demo/common.sh
 
-if [[ -z $1 ]]; then # no network argument, use default
-  entrypoint=()
+if [[ -z $1 ]]; then # no network argument, use localhost by default
+  entrypoint=(--url http://127.0.0.1:8899)
 else
   entrypoint=("$@")
 fi