Attempt to reinstate Value [failed](Refs #51)[3]

* Updated compilerOptions in tsconfig.json - target: es2016 -> es2020
    Reason: support for bigInt(0n)
* stash.ts - Reintroduce Value to be passed to visitors in pyvisitor
    Updates: Failed lol, major changes that affects stdlib in src
    Temp solution: fallback to Value : any in /cse-machine/stash.ts for now
* py_operators.ts - introduce bool for integers, string, None
  (evaluteUnaryExpression)
* py_operator.ts refactored {evaluateBinaryExpression} - cleaner sequence
    Operands: String -> Complex -> Mixed Float&/Int (arithmetic ->
    comparisons) -> Integers only
* py_visitor.ts: added visitComplexExpr

Author: lucasnyc

src/cse-machine/py_interpreter.ts

@@ -3,6 +3,7 @@ import { CSEBreak, Representation, Result, Finished } from "../types";
 import { StmtNS } from "../ast-types";
 import { Value, ErrorValue } from "./stash";
 import { PyVisitor } from "./py_visitor";
+import { toPythonString } from "../stdlib";
 
 type Stmt = StmtNS.Stmt;
 
@@ -15,7 +16,7 @@ export function PyCSEResultPromise(context: Context, value: Value): Promise<Resu
             const representation = new Representation(errorValue.message);
             resolve({ status: 'finished', context, value, representation } as Finished);
         } else {
-            const representation = new Representation(value);
+            const representation = new Representation(toPythonString(value));
             resolve({ status: 'finished', context, value, representation } as Finished);
         }
     });