tests: rename pointer_arithmetic_should_be_checked.vv -> unsafe_required.vv (#5897)

vlib/v/checker/tests/unsafe_required.out

@@ -0,0 +1,34 @@
+vlib/v/checker/tests/unsafe_required.v:4:6: error: pointer arithmetic is only allowed in `unsafe` blocks
+    2 |     v := 5
+    3 |     mut p := &v
+    4 |     p++
+      |      ~~
+    5 |     p += 2
+    6 |     _ := v
+vlib/v/checker/tests/unsafe_required.v:5:7: error: pointer arithmetic is only allowed in `unsafe` blocks
+    3 |     mut p := &v
+    4 |     p++
+    5 |     p += 2
+      |       ~~
+    6 |     _ := v
+    7 | }
+vlib/v/checker/tests/unsafe_required.v:11:14: error: pointer arithmetic is only allowed in `unsafe` blocks
+    9 | fn test_ptr_infix() {
+   10 |     v := 4
+   11 |     mut q := &v - 1
+      |              ^
+   12 |     q = q + 3
+   13 |     _ := q
+vlib/v/checker/tests/unsafe_required.v:12:9: error: pointer arithmetic is only allowed in `unsafe` blocks
+   10 |     v := 4
+   11 |     mut q := &v - 1
+   12 |     q = q + 3
+      |         ^
+   13 |     _ := q
+   14 |     _ := v
+vlib/v/checker/tests/unsafe_required.v:24:7: error: method `S1.f` must be called from an `unsafe` block
+   22 | fn test_funcs() {
+   23 |     s := S1{}
+   24 |     s.f()
+      |       ~~~
+   25 | }

vlib/v/checker/tests/unsafe_required.vv

@@ -0,0 +1,25 @@
+fn test_ptr_assign() {
+    v := 5
+    mut p := &v
+    p++
+    p += 2
+    _ := v
+}
+
+fn test_ptr_infix() {
+    v := 4
+    mut q := &v - 1
+    q = q + 3
+    _ := q
+    _ := v
+}
+
+struct S1 {}
+
+[unsafe_fn]
+fn (s S1) f(){}
+
+fn test_funcs() {
+    s := S1{}
+    s.f()
+}