RFR: 8310843: Reimplement ByteArray and ByteArrayLittleEndian with Unsafe [v5]

[Glavo]

> `ByteArray` and `ByteArrayLittleEndian` are very useful tool classes that can be used in many places to performance tuning.
> 
> Currently they are implemented by `VarHandle`, so using them may have some impact on startup time.
> 
> This PR reimplements them using `Unsafe`, which reduces the impact on startup time.

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

 - delete extraneous whitespace
 - add javadoc

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Changes:
  - all: https://git.openjdk.org/jdk/pull/14636/files
  - new: https://git.openjdk.org/jdk/pull/14636/files/8c3a2087..4ac26325

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=14636&range=04
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=14636&range=03-04

  Stats: 8 lines in 1 file changed: 8 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/14636.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14636/head:pull/14636

PR: https://git.openjdk.org/jdk/pull/14636