Add lodash GroupBy as taint step

[Vasco-jofra]

Adds _.groupBy as a taint step.

This is analogous to the GroupByTaintStep class, which does the same for Object and Map.

https://github.com/github/codeql/blob/d83cbde1cb1263fb476a55ea5fd7972307138905/javascript/ql/lib/semmle/javascript/Collections.qll#L158C1-L166C4

[asgerf]

The relevant implementation for Map.groupBy is here:

codeql/javascript/ql/lib/semmle/javascript/internal/flow_summaries/Maps.qll

Lines 130 to 139 in 93c891a

	override predicate propagatesFlow(string input, string output, boolean preservesValue) {
	preservesValue = true and
	(
	input = "Argument[0].ArrayElement" and
	output = ["Argument[1].Parameter[0]", "ReturnValue.MapValue.ArrayElement"]
	or
	input = "Argument[1].ReturnValue" and
	output = "ReturnValue.MapKey"
	)
	}

This would be the closest matching implementation for _.groupBy I think:

   preservesValue = true and
   input = "Argument[0].ArrayElement" and 
   output = ["Argument[1].Parameter[0]", "ReturnValue.AnyMember.ArrayElement"] 

Note that there is currently no content corresponding to MapKey for the keys of a plain object.