Add necessary SKIPIFs to new phpdbg tests

Similarly to other watchpoint tests, we add SKIPIFs.
These TRACKED_ALLOC issues should be investigated though [1] [2].

[1] de5c760#comments
[2] #15229 (review)

Author: ndossche

sapi/phpdbg/tests/gh15210_001.phpt

@@ -1,5 +1,11 @@
 --TEST--
 GH-15210 use after free after continue
+--SKIPIF--
+<?php
+if (getenv('SKIP_ASAN')) {
+    die("skip intentionally causes segfaults");
+}
+?>
 --PHPDBG--
 b 4
 r

sapi/phpdbg/tests/gh15210_002.phpt

@@ -1,5 +1,11 @@
 --TEST--
 GH-15210 use after free after continue
+--SKIPIF--
+<?php
+if (getenv('SKIP_ASAN')) {
+    die("skip intentionally causes segfaults");
+}
+?>
 --PHPDBG--
 b 4
 r