RFR: 8295658 G1: Refactor G1SegmentedArray to indicate that it is an allocator [v2]

[Ivan Walulya]

> Hi,
> 
> Please review this refactoring change of G1SegmentedArray to G1MonotonicArena which is a more appropriate name for the intended use of the class objects.
> 
> The change has two commits, with the first commit refactoring the class names and the second commit adding the corresponding changes to file names. 
> 
> Testing: builds

Ivan Walulya has updated the pull request incrementally with one additional commit since the last revision:

  Thomas review

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/10767/files
  - new: https://git.openjdk.org/jdk/pull/10767/files/48be550f..5de77499

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=10767&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=10767&range=00-01

  Stats: 15 lines in 5 files changed: 0 ins; 2 del; 13 mod
  Patch: https://git.openjdk.org/jdk/pull/10767.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10767/head:pull/10767

PR: https://git.openjdk.org/jdk/pull/10767