Add Lexer to Python bindings

**Is your feature request related to the C++ slang project or the pyslang Python bindings?**
Pyslang Python bindings

**Is your feature request related to a problem? Please describe.**
Add Lexer for pyslang based on Discussion #1387 

**Describe the solution you'd like**
Please add Lexer to pyslang bindings

**Describe alternatives you've considered**
N/A

**Additional context**
