Extend the gc+heap=debug messages to also show the number of failed regions of that category.

E.g. for these messages
```
[1.912s][info ][gc,heap      ] GC(0) Eden regions: 64->0(56)
[1.912s][info ][gc,heap      ] GC(0) Survivor regions: 0->8(8)
[1.912s][info ][gc,heap      ] GC(0) Old regions: 0->56
[1.912s][info ][gc,heap      ] GC(0) Archive regions: 2->2
[1.912s][info ][gc,heap      ] GC(0) Humongous regions: 5->5
```

to add something like

```
[1.912s][info ][gc,heap      ] GC(0) Eden regions: 64->0(56) [0]
[1.912s][info ][gc,heap      ] GC(0) Survivor regions: 0->8(8) [3]
[1.912s][info ][gc,heap      ] GC(0) Old regions: 0->56 [2]
[1.912s][info ][gc,heap      ] GC(0) Archive regions: 2->2 [0]
[1.912s][info ][gc,heap      ] GC(0) Humongous regions: 5->5 [2]
```



This is one of the follow-up tasks discussed at :
 - https://github.com/openjdk/jdk/pull/6627#pullrequestreview-821445879, and
 - https://github.com/openjdk/jdk/pull/6627#issuecomment-985478359