RFR: 8252041: G1: Fix incorrect uses of HeapRegionManager::max_length [v3]

[Thomas Schatzl]

> Hi all,
> 
>   can I have reviews for this change that fixes some uses of HeapRegionManager::max_regions()/max_expandable_regions() in
>   our code to use the correct variant?
> 
> HeapRegionManager::max_length gives the absolute maximum number of regions reserved for the heap based on the
> reservation.
> HeapRegionmanager::max_expandable_regions() returns the maximum number of regions the heap can grow to (can be
> committed).
> Typically they are exchangeable, but if the reservation is larger than what -Xmx allows (like when file-mapping old
> gen), this is not the case, and causes assertions. In some cases the existing region manager code could (if it reserved
> more than -Xmx) give back more than -Xmx allows.  Testing: tier1-5.

Thomas Schatzl has updated the pull request with a new target base due to a merge or a rebase. The pull request now
contains three commits:

 - Merge branch 'master' into 8252041-incorrect-use-of-max-length
 - Renaming
 - Initial import

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Changes: https://git.openjdk.java.net/jdk/pull/178/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=178&range=02
  Stats: 118 lines in 15 files changed: 15 ins; 0 del; 103 mod
  Patch: https://git.openjdk.java.net/jdk/pull/178.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/178/head:pull/178

PR: https://git.openjdk.java.net/jdk/pull/178