[WIP][Env] Fin-env

[ianhajra]

What does this PR do?

Financial backtesting environment for stable-worldmodel with comprehensive trading features and out-of-distribution testing capabilities.

Before submitting

• Did you read the contributor guideline, Pull Request section?
• Did you make sure to update the documentation with your changes? Here are the documentation guidelines
• Did you write any new necessary tests?

Implementation Status

Completed

• Financial environment framework with action/observation spaces
• Simplified variation system ready for dynamic market data integration
• Portfolio management and trading logic (buy/sell/hold)
• Backtesting results calculation (returns, Sharpe ratio, drawdown)
• Time machine functionality for date-specific backtesting
• All image/rendering dependencies removed and replaced with financial data TODOs
• Environment registration in stable-worldmodel framework

Who can review?

@lucas-maes can review

[lucas-maes]

• No need to add test that are env specific in the test_wrapper.py