tests/extmod: Add test for ure debug printing when compiling a regex.

tests/extmod/ure_debug.py

+# test printing debugging info when compiling
+import ure
+ure.compile('^a|b[0-9]\w$', ure.DEBUG)

tests/extmod/ure_debug.py.exp

+ 0: rsplit 5 (3)
+ 2: any
+ 3: jmp 0 (-5)
+ 5: save 0
+ 7: split 14 (5)
+ 9: assert bol
+10: char a
+12: jmp 23 (9)
+14: char b
+16: class 1 0x30-0x39
+20: namedclass w
+22: assert eol
+23: save 1
+25: match
+Bytes: 26, insts: 14