RFR: 8252374: Add a new factory method to concatenate a sequence of BodyPublisher instances into a single publisher. [v5]

[Daniel Fuchs]

> Continuing the review with a PR...
> 
> 8252374: Add a new factory method to concatenate a sequence
>          of BodyPublisher instances into a single publisher.
> https://bugs.openjdk.java.net/browse/JDK-8252374
> 
> 
> Draft CSR:
> https://bugs.openjdk.java.net/browse/JDK-8252382

Daniel Fuchs has updated the pull request incrementally with one additional commit since the last revision:

  Improved API documentation, added more tests for contentLength()

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/57/files
  - new: https://git.openjdk.java.net/jdk/pull/57/files/dfbc646d..e68faf41

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=57&range=04
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=57&range=03-04

  Stats: 76 lines in 2 files changed: 73 ins; 2 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/57.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/57/head:pull/57

PR: https://git.openjdk.java.net/jdk/pull/57