fix: spl-token-sale-tutorial add missing helper functions in test setup

[0xRektified]

Add missing helper functions in token sale tutorial

Summary

This PR adds the missing helper function definitions (toRawTokenAmount, toDisplayAmount, and lamportsToSol) that are used throughout the test cases but were never defined in the tutorial.

Problem

Users following the tutorial would encounter errors when running the tests because these helper functions are called in multiple places:

• lamportsToSol(solToSend) and toDisplayAmount(expectedTokenAmount)
• toRawTokenAmount(1000)
• toDisplayAmount(currentSupply) and toDisplayAmount(remainingSupply)
• toRawTokenAmount(20)
• lamportsToSol() calls

Solution

Added three helper functions at the beginning of the test file (after imports, before the describe block):

1. toRawTokenAmount(amount: number)
2. toDisplayAmount(amount: number)
3. lamportsToSol(lamports: number | anchor.BN)

Testing

Users can now successfully run all test cases without encountering "function not defined" errors.