RFR: 8272723: Don't use Access API to access primitive fields [v3]

[Roman Kennke]

> For earlier incarnations of Shenandoah, we needed to put barriers before accessing primitive fields. This is no longer necessary nor implemented/used by any GC, and we should simplify the code to do plain access instead.
> 
> (We may want to remove remaining primitive access machinery in the Access API soon)
> 
> Testing:
>  - [x] tier1
>  - [ ] tier2
>  - [ ] hotspot_gc

Roman Kennke 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 seven additional commits since the last revision:

 - Merge branch 'master' into JDK-8272723
 - Remove redundant asserts
 - Revert to use RawAccess<MO_SEQ_CST> for volatile accesses
 - Fix alignment
 - Consolidate (obj)field_addr() variants
 - Remove remaining primitive Access API uses
 - 8272723: Don't use Access API to access primitive fields

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/5187/files
  - new: https://git.openjdk.java.net/jdk/pull/5187/files/82366c30..3aff84ab

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=5187&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=5187&range=01-02

  Stats: 273 lines in 22 files changed: 115 ins; 110 del; 48 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5187.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5187/head:pull/5187

PR: https://git.openjdk.java.net/jdk/pull/5187