feat(inspect): add deepMap function

[Duologic]

I've written this function at least twice, figured it would be useful as part of xtd.

[jdbaldry]

Do we want to enforce that in function?

[Duologic]

Jsonnet will error out anyway, this is more of a warning than it is a rule.

[jdbaldry]

Should deepMap recurse first before applying func? At the moment we have a pre-order traversal, is that what people would expect? If their func modifies x, then we may never recurse into the children.

[Duologic]

This worked for my use cases, another solution might work as well.

Would you do this instead?

Suggested change

	deepMap(func, x):
	if std.isObject(x)
	then std.mapWithKey(function(_, y) self.deepMap(func, y), func(x))
	else if std.isArray(x)
	then std.map(function(y) self.deepMap(func, y), func(x))
	else func(x),
	deepMap(func, x):
	func(
	if std.isObject(x)
	then std.mapWithKey(function(_, y) self.deepMap(func, y), x)
	else if std.isArray(x)
	then std.map(function(y) self.deepMap(func, y), x)
	else x
	),

[jdbaldry]

To be honest, I'm really not sure what traversal people would expect. I can't remember the last time I performed a map over trees. I guess we can just document what traversal it is and people can use that to decide if this does what they want.

[Duologic]

I'm inclined to apply this suggestion, it'll allow to drop the comment about return type as that would only apply if we execute func early. One less way to fail I guess.

[jdbaldry]

Nice