RFR: Improved timing reports

[William Kemper]

This is a bundle of a few minor changes to the cycle and global timing reports:
* Render coalescing phase closer to where it happens in the cycle
* Include timing for remembered set swap and satb management during init mark pause
* Emit a cycle report for old generation's bootstrap cycle
* Track old GC cycles completed and interrupted for global report

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

Commit messages:
 - Keep track of completed and interrupted old GC counts
 - Emit separate report for old GC's bootstrap cycle
 - Add phase timing for rset swap and satb transfer
 - Report coalescing phase in timing report closer to the order in which it happens

Changes: https://git.openjdk.java.net/shenandoah/pull/131/files
 Webrev: https://webrevs.openjdk.java.net/?repo=shenandoah&pr=131&range=00
  Stats: 89 lines in 6 files changed: 58 ins; 27 del; 4 mod
  Patch: https://git.openjdk.java.net/shenandoah/pull/131.diff
  Fetch: git fetch https://git.openjdk.java.net/shenandoah pull/131/head:pull/131

PR: https://git.openjdk.java.net/shenandoah/pull/131