Withdraw authority no longer implies a custodian (#11302)

* Withdraw authority no longer implies a custodian

Before this change, if the withdraw authority and custodian had
the same public key, then a withdraw authority signature would
imply a custodian signature and lockup would be not be enforced.

After this change, the client's withdraw instruction must
explictly reference a custodian account in its optional sixth
account argument.

Likewise, the fee-payer no longer implies either a withdraw
authority or custodian.

* Fix test

The test was configuring the stake account with the fee-payer as
the withdraw authority, but then passing in a different key to
the withdraw instruction's withdraw authority parameter. It only
worked because the second transaction was signed by the fee-payer.

stake-monitor/src/lib.rs

@@ -452,7 +452,7 @@ mod test {
         let instructions = stake_instruction::create_account(
             &payer.pubkey(),
             &stake3_keypair.pubkey(),
-            &Authorized::auto(&payer.pubkey()),
+            &Authorized::auto(&stake3_keypair.pubkey()),
             &Lockup::default(),
             one_sol,
         );