Scripting tests

[ivan-mogilko]

We have compiler tests in the main repo, but these test only that the script compiler does something expected.

We need runtime script tests to know that the scripts are executed as expected.

The purpose of such tests should be testing various script constructs and expressions, with the minimal necessary api calls:

• variables assigned and read;
• arithmetic operations;
• arrays, creating, writing, reading;
• dynamic arrays;
• nested elements in structs
• function calls, passing parameters, reading return values
• and so on.