test(awk): add spec tests for delete array (already implemented) (#820)

Verify delete array (without subscript) works. Feature was already implemented.\n\nCloses #798

Author: chaliy

crates/bashkit/tests/spec_cases/awk/delete-array.test.sh

@@ -0,0 +1,21 @@
+### awk_delete_entire_array
+# delete array clears all elements
+echo "test" | awk 'BEGIN{a[1]=1; a[2]=2; a[3]=3; delete a; print length(a)}'
+### expect
+0
+### end
+
+### awk_delete_single_element
+# delete array[key] removes one element
+echo "test" | awk 'BEGIN{a[1]=1; a[2]=2; a[3]=3; delete a[2]; for(k in a) print k, a[k]}' | sort
+### expect
+1 1
+3 3
+### end
+
+### awk_delete_multiple_arrays
+# delete works on multiple arrays
+echo "test" | awk 'BEGIN{a[1]=1; b[1]=2; delete a; delete b; print length(a), length(b)}'
+### expect
+0 0
+### end