add extra validation to withdraw spl token instruction

[brewmaster012]

• add mint_account (the SPL token id, analogous to ERC20 address) to the accounts, and validate the associated token address (ATA) of the PDA address as the from in the SPL token transfer.
• add decimals to the instruction parameter
• use transfer_checked instead of transfer for additional validation

These redundant validation can prevent accidental programming error and reduce potential attack surface.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 13 lines in your changes missing coverage. Please review.

Project coverage is 8.30%. Comparing base (812ec18) to head (e340809).

Files with missing lines	Patch %	Lines
programs/protocol-contracts-solana/src/lib.rs	0.00%	13 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##            main     #39      +/-   ##
========================================
- Coverage   8.60%   8.30%   -0.31%     
========================================
  Files          1       1              
  Lines        244     253       +9     
========================================
  Hits          21      21              
- Misses       223     232       +9     

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