Evaluating a Key Path on a value for IndexedDB is missing some cases

[rasviitanen]

The function for evaluating a key path on a value is missing some cases and does not have proper error handeling.
The function uses direct bindings to spidermonkey, so we are able to salvage a lot of the implementation from gecko.

Task

• Create a complete evaluation function

Function
evaluate_key_path_on_value

Files
compontens/script/dom/idbobjectstore.rs

Useful links
https://www.w3.org/TR/IndexedDB-2/#evaluate-a-key-path-on-a-value
https://github.com/mozilla/gecko-dev/blob/master/dom/indexedDB/KeyPath.cpp#L58-L256