Merge 'builtins/str_length' and 'builtins/list_length' test cases

Author: HugoGGuerrier

testsuite/tests/interpreter/builtins/length/script.lkql

@@ -0,0 +1,3 @@
+val o = select o @ ObjectDecl
+print(o.length)
+print("Hello".length)

…nterpreter/builtins/list_length/test.out …sts/interpreter/builtins/length/test.outtestsuite/tests/interpreter/builtins/list_length/test.out renamed to testsuite/tests/interpreter/builtins/length/test.out testsuite/tests/interpreter/builtins/list_length/test.out renamed to testsuite/tests/interpreter/builtins/length/test.out

@@ -1 +1,2 @@
 2
+5