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

[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

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Commit messages:
 - 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: https://git.openjdk.java.net/jdk/pull/3434/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3434&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8199407
  Stats: 28 lines in 4 files changed: 19 ins; 1 del; 8 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