RFR: 8302790: Set FileMapRegion::mapped_base() to null if mapping fails [v3]

[Matias Saavedra Silva]

> For cleanliness, we should reset FileMapRegion::mapped_base() to nullptr in case the mapping fails for any reasons. This patch moves the `set_mapped_base()` call after all the checks complete so it can remain as null in case checks fail. Verified with tier 1-5 tests.

Matias Saavedra Silva 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 five additional commits since the last revision:

 - Merge branch 'master' into mapped_base_8302790
 - Used consistent pattern
 - Merge branch 'master' into mapped_base_8302790
 - Moved assignment after checks
 - 8302790: Set FileMapRegion::mapped_base() to null if mapping fails

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/16866/files
  - new: https://git.openjdk.org/jdk/pull/16866/files/e15aae2d..1f5b8ada

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=16866&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=16866&range=01-02

  Stats: 10371 lines in 345 files changed: 7958 ins; 1684 del; 729 mod
  Patch: https://git.openjdk.org/jdk/pull/16866.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16866/head:pull/16866

PR: https://git.openjdk.org/jdk/pull/16866