Split evaluate into two phases - Parse and Evaluate

[ppaska]

We need to split evaluation into two phases:

• parse - what parses script (text) and returns AST
• evaluate - takes AST and execute each instruction.

This should significantly improve performance as well as add more flexibility for usage scenarios

Good articles worth reading:

1. https://greentreesnakes.readthedocs.io/en/latest/

• https://astexplorer.net/

2. https://ruslanspivak.com/lsbasi-part7/
3. https://python-ast-explorer.com/