Filterx function path lookup

[bshifter]

Add path_lookup to the filterx_object Namespace as an Alternative to get_subscript

This PR introduces a new function, path_lookup, to the filterx_object namespace. It allows retrieving elements from nested filterx lists or dictionaries in a single call, providing a more convenient and expressive alternative to using get_subscript repeatedly.

Key Features:

• Flexible First Argument: The first argument must be a list or dictionary. Mixed structures (e.g., nested combinations of lists and dictionaries) are fully supported.
• Dynamic Path Lookup: The second parameter accepts a list literal containing both filterx strings (for dictionary keys) and integers (for list indices).
• Deep Nested Access: Enables seamless access to deeply nested elements in hybrid list-dictionary structures.
• Reverse Indexing Support: Integer indices support negative values for reverse indexing in lists, mirroring Python-like behavior.

example:

filterx {
d = {"foo":1,"bar":[3,2,1],"baz":{"tik":"tak"}};
a = path_lookup(d, ["bar", 0]); # returns 3
b = path_lookup(d, ["baz", "tik"]); # returns "tak"
c = path_lookup(d, ["bar", -1]); # returns 1
}