oracles - optimized defi contract, and test script, fixed error links

[Phenzic]

Problem

• The original Solana code lacked consistency, clear naming conventions, and descriptive documentation, which could hinder readability and maintainability.

Summary of Changes

I full name variables according to the guide (e.g., escrow_amt to escrow_amount), I replaced magic numbers with named constants, and detailed comments were added to enhance code clarity and organization.

Fixes #1: Improved variable names for clarity and consistency. Fixes #2: Replaced magic numbers with named constants and added descriptive comments. Fixes #3: I replaced the test script to have a consistent error handler, and optimized it to avoid repetitions