RFR: 8292566: Add reference to the java.nio.file package in java.nio package documentation [v3]

[Brian Burkhalter]

> Add a phrase about `java.nio.file` to the sentence in the `java.nio` package documentation describing its subpackages.

Brian Burkhalter has updated the pull request incrementally with one additional commit since the last revision:

  8292566: Reduce central abstractions to Path and Files

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Changes:
  - all: https://git.openjdk.org/jdk/pull/9910/files
  - new: https://git.openjdk.org/jdk/pull/9910/files/53cdc086..e7243777

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=9910&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=9910&range=01-02

  Stats: 20 lines in 1 file changed: 0 ins; 12 del; 8 mod
  Patch: https://git.openjdk.org/jdk/pull/9910.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9910/head:pull/9910

PR: https://git.openjdk.org/jdk/pull/9910