RFR: 8299513: Clean up java.io [v7]

[Per Minborg]

> Code in java.io contains many legacy constructs and semantics not recommended including: 
> 
> * C-style array declaration 
> * Unnecessary visibility 
> * Redundant keywords in interfaces (e.g. public, static) 
> * Non-standard naming for constants 
> * Javadoc typos 
> * Missing final declaration 
> 
> These should be fixed as a sanity effort.

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

 - Update src/java.base/share/classes/java/io/ObjectStreamConstants.java
   
   Co-authored-by: Andrey Turbanov <turbanoff at gmail.com>
 - Clean up ObjectStreamConstants

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/11848/files
  - new: https://git.openjdk.org/jdk/pull/11848/files/f231c16b..33cdd8f1

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=11848&range=06
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=11848&range=05-06

  Stats: 22 lines in 3 files changed: 0 ins; 0 del; 22 mod
  Patch: https://git.openjdk.org/jdk/pull/11848.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11848/head:pull/11848

PR: https://git.openjdk.org/jdk/pull/11848