Fix node2code for array indexing expressions

[aparajit-pratap]

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Purpose

Fixes node2code for array indexing expressions. Previously n2c would transform an array indexing expression to this:

arr[2]; => DesignScript.BuiltIn.Get.ValueAtIndex(arr, 2);

Even though behind the scenes this transformation is necessary to invoke the ZT function, for the user it doesn't make sense when they are trying to understand the DesignScript in the resulting code block. After this change, it doesn't transform such expressions to the ZT function call in the backend anymore. This also prevents a crash from occurring when more complex expressions such as this were transformed:

p[2].DistanceTo(p[3]); => DesignScript.BuiltIn.Get.ValueAtIndex(p, 2).DistanceTo(DesignScript.BuiltIn.Get.ValueAtIndex(p, 3));

Future TODOs:

• The same issue exists for other cases, where the conversion to the backend function call can be avoided, for example, dictionary expressions:

{string_exp1 : exp2} => DesignScript.Builtin.Dictionary.ByKeysValues([string_exp1], [exp2]);

• Similar expressions in Imperative blocks still convert to backend function calls

Declarations

Check these if you believe they are true

• The codebase is in a better state after this PR
• Is documented according to the standards
• The level of testing this PR includes is appropriate
• User facing strings, if any, are extracted into *.resx files
• All tests pass using the self-service CI.
• Snapshot of UI changes, if any.
• Changes to the API follow Semantic Versioning and are documented in the API Changes document.
• This PR modifies some build requirements and the readme is updated

Release Notes

Fixes Node To Code for list indexing expressions.

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