fix(sdk): defining function behavior in eval is not consistent with the original product

[ihexxa]

Add ability for running eval() where it adds functions that can be then called later on from the same pre-request/after-response script the eval() first happened. (For feature parity with other API clients and Node.js itself)

Example:

const code = `
function get_some_string() {
  return 'aaaa';
}
`;

eval(code);

console.log(get_some_string()); 

Closes INS-4668