RFR: JDK-8300582: Introduce interface for unaligned memory accesses [v4]

[Justin King]

> Introduce interface for unaligned memory accesses `UnalignedAccess`, consolidate the byte swapping implementation to `byteswap`, and switch to a generic implementation of `Bytes`.

Justin King has updated the pull request incrementally with two additional commits since the last revision:

 - Fix typo
   
   Signed-off-by: Justin King <jcking at google.com>
 - Fix compilation
   
   Signed-off-by: Justin King <jcking at google.com>

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/12078/files
  - new: https://git.openjdk.org/jdk/pull/12078/files/2c4d91eb..793c7718

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=12078&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=12078&range=02-03

  Stats: 4 lines in 1 file changed: 3 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/12078.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12078/head:pull/12078

PR: https://git.openjdk.org/jdk/pull/12078