RFR: 8314896: additional clarifications to reversed() default methods' implementation requirements [v2]

[Stuart Marks]

> Wording changes to make clear that the scenarios described are merely examples and are not normative requirements.

Stuart Marks 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 two additional commits since the last revision:

 - Merge branch 'master' into JDK-8314896-more-reversed-clarifications
 - Update wording for {Deque,List,SortedMap,SortedSet}.reversed implSpecs.

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Changes:
  - all: https://git.openjdk.org/jdk/pull/15799/files
  - new: https://git.openjdk.org/jdk/pull/15799/files/064bc649..f88d0cba

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=15799&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=15799&range=00-01

  Stats: 95017 lines in 2630 files changed: 38584 ins; 18471 del; 37962 mod
  Patch: https://git.openjdk.org/jdk/pull/15799.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15799/head:pull/15799

PR: https://git.openjdk.org/jdk/pull/15799