RFR: 8316734: URLEncoder should specify that replacement bytes will be used in case of coding error [v2]

[Darragh Clarke]

> Currently the descriptions of `URLEncoder.encode` and `URLDecoder.decode` don't specify their use of replacement bytes or replacement character when they cannot handle a character or sequence of bytes. This is longstanding behavior but needs to be documented.
> 
> **Solution**
> - Added a new line to `URLEncoder.encode` API documentation to document that the charset's replacement bytes are used.
> 
> - Also changed `URLDecoder.decode` API documentation to document its use of the charset's replacement character, also changed some wording.

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

 - cleanup
 - implemented feedback

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/16709/files
  - new: https://git.openjdk.org/jdk/pull/16709/files/881b56e1..2ee3f715

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=16709&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=16709&range=00-01

  Stats: 17 lines in 1 file changed: 6 ins; 10 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/16709.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16709/head:pull/16709

PR: https://git.openjdk.org/jdk/pull/16709