RFR: 8308016: Use snippets in java.io package [v7]

[Brian Burkhalter]

> Replace `<pre>{@code ...}</pre>` patterns and the like with `{@snippet lang=java : ...}`.

Brian Burkhalter has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains seven additional commits since the last revision:

 - Merge
 - 8308016: Reinstate @snippet for RandomAccessFile::readLong
 - 8308016: Reduce linking in File::toPath snippet
 - 8308016: Fix link in snippet of File::toPath
 - 8308016: Address reviewer comments since previous commit
 - 8308016: Remove ellipses ("...") from snippets
 - 8308016: Use snippets in java.io package

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/13957/files
  - new: https://git.openjdk.org/jdk/pull/13957/files/8ae42cf2..d0dce640

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13957&range=06
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13957&range=05-06

  Stats: 13770 lines in 553 files changed: 8566 ins; 1596 del; 3608 mod
  Patch: https://git.openjdk.org/jdk/pull/13957.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13957/head:pull/13957

PR: https://git.openjdk.org/jdk/pull/13957