[token-cli] Reduce number of transactions for confidential transfer withdraw

[samkim-crypto]

Problem

The withdraw-confidential-tokens command is currently executed in a sequence of 4 transactions:

1. system instruction to create the proof context account
2. verify and store the proof context account
3. execute the withdraw
4. close the proof context account

Due to the transaction size limit, steps 1 and 2 must be independent transactions. However, steps 3 and 4 can still be executed in a single transaction.

Proposed solution

Update the token-client to merge the instructions in steps 3 and 4. This change should also be applied for other instructions that uses proof context such as ConfigureAccount.