RFR: 8217327: G1 Post-Cleanup region liveness printing should not print out-of-date efficiency

[Joakim Nordström]

**Description**
This fix addresses the issue where gc-efficiency is printed incorrectly when logging post-marking and post-cleanup. The gc-efficiency is calculated in the end of the marking phase, to be logged in the post-cleanup section. It is however not reset, meaning that next phase's post-marking log will show the old value.

- The gc-efficiency is initialized to -1 when it hasn't been calculated.
- Negative gc-efficiency is displayed as a hyphen "-" in the summary.
- The gc-efficiency is reset to -1 in `HeapRegion::note_start_of_marking()`

**Note:** there is a sister issue that moves the post-cleanup printing to a later stage. Without this fix, the logging will still be incorrect, so both fixes are needed. See: [JDK-8260042: G1 Post-cleanup liveness printing occurs too early](https://github.com/openjdk/jdk/pull/2168)

This fix has been tested together with the above mentioned fix.

**Example**
This is what logging like after fix has been applied.
### PHASE Post-Marking @ 410.303
### HEAP  reserved: 0x0ffc00000-0x100000000  region-size: 1048576
###
###   type           address-range       used  prev-live  next-live          gc-eff     remset   state  code-roots
###                                                 (bytes)    (bytes)    (bytes)      (bytes/ms)    (bytes)            (bytes)
###   OLD  0x0ffc00000-0x0ffd00000    1048368    1048368    1048368               -       8464   UPDAT       6096
###   OLD  0x0ffd00000-0x0ffe00000     132856     132856     132856               -       2544   UPDAT         16
###   SURV 0x0ffe00000-0x0fff00000      21368      21368      21368               -       2544   CMPLT         16
###   FREE 0x0fff00000-0x100000000          0          0          0               -       2384   UNTRA         16
###
### SUMMARY  capacity: 4.00 MB  used: 1.15 MB / 28.67 %  prev-live: 1.15 MB / 28.67 %  next-live: 1.15 MB / 28.67 %  remset: 0.02 MB  code-roots: 0.01 MB
### PHASE Post-Cleanup @ 410.305
### HEAP  reserved: 0x0ffc00000-0x100000000  region-size: 1048576
###
###   type           address-range       used  prev-live  next-live          gc-eff     remset   state  code-roots
###                                                 (bytes)    (bytes)    (bytes)      (bytes/ms)    (bytes)            (bytes)
###   OLD  0x0ffc00000-0x0ffd00000    1048368    1048368    1048368               -       8624   UNTRA       6096
###   OLD  0x0ffd00000-0x0ffe00000     132856     132856     132856       1352923.9       2544   CMPLT         16
###   SURV 0x0ffe00000-0x0fff00000      21368      21368      21368               -       2544   CMPLT         16
###   FREE 0x0fff00000-0x100000000          0          0          0               -       2384   UNTRA         16
###
### SUMMARY  capacity: 4.00 MB  used: 1.15 MB / 28.67 %  prev-live: 1.15 MB / 28.67 %  next-live: 1.15 MB / 28.67 %  remset: 0.02 MB  code-roots: 0.01 MB
### PHASE Post-Marking @ 450.310
### HEAP  reserved: 0x0ffc00000-0x100000000  region-size: 1048576
###
###   type           address-range       used  prev-live  next-live          gc-eff     remset   state  code-roots
###                                                 (bytes)    (bytes)    (bytes)      (bytes/ms)    (bytes)            (bytes)
###   OLD  0x0ffc00000-0x0ffd00000    1048368    1048368    1048368               -       8624   UPDAT       6096
###   OLD  0x0ffd00000-0x0ffe00000     174456     174456     174456               -       2544   UPDAT         16
###   SURV 0x0ffe00000-0x0fff00000      21368      21368      21368               -       2544   CMPLT         16
###   FREE 0x0fff00000-0x100000000          0          0          0               -       2384   UNTRA         16
###
### SUMMARY  capacity: 4.00 MB  used: 1.19 MB / 29.66 %  prev-live: 1.19 MB / 29.66 %  next-live: 1.19 MB / 29.66 %  remset: 0.02 MB  code-roots: 0.01 MB
### PHASE Post-Cleanup @ 450.312
### HEAP  reserved: 0x0ffc00000-0x100000000  region-size: 1048576
###
###   type           address-range       used  prev-live  next-live          gc-eff     remset   state  code-roots
###                                                 (bytes)    (bytes)    (bytes)      (bytes/ms)    (bytes)            (bytes)
###   OLD  0x0ffc00000-0x0ffd00000    1048368    1048368    1048368               -       8624   UNTRA       6096
###   OLD  0x0ffd00000-0x0ffe00000     174456     174456     174456       1266519.2       2544   CMPLT         16
###   SURV 0x0ffe00000-0x0fff00000      21368      21368      21368               -       2544   CMPLT         16
###   FREE 0x0fff00000-0x100000000          0          0          0               -       2384   UNTRA         16
###

**Testing**
- Manual testing
- hs-tier1, hs-tier2

-------------

Commit messages:
 - Clear gc_efficiency by setting to -1. Print "-" when gc efficieny is negative.

Changes: https://git.openjdk.java.net/jdk/pull/2217/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=2217&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8217327
  Stats: 22 lines in 3 files changed: 17 ins; 0 del; 5 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2217.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2217/head:pull/2217

PR: https://git.openjdk.java.net/jdk/pull/2217