RFR: 8199407: Skip Rebuild Remset Phase if there are no rebuild candidates [v2]

[Ivan Walulya]

> Hi all,
> 
> Please review this change that skips the rebuild remset phase and the associated updates after rebuild, If during Remark, G1 finds that there are no remembered sets to rebuild.
> 
> Test: tier1-5

Ivan Walulya has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains eight additional commits since the last revision:

 - Fix issues raised in Thomas review, and add test
 - Merge remote-tracking branch 'upstream/master' into JDK-8199407
 - remove trailing white space
 - Merge branch 'master' into JDK-8199407
 - variable name refactor
 - variable name refactor
 - skip iterations that depend on total_selected_for_rebuild
 - skip the rebuild remembered set phase if remark did not select any regions for rebuilding

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/3434/files
  - new: https://git.openjdk.java.net/jdk/pull/3434/files/9022646e..b9233696

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=3434&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=3434&range=00-01

  Stats: 39977 lines in 1660 files changed: 8245 ins; 27492 del; 4240 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3434.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3434/head:pull/3434

PR: https://git.openjdk.java.net/jdk/pull/3434