RFR: JDK-8305713: DocCommentParser: merge blockContent and inlineContent [v6]

[Jonathan Gibbons]

> Please review a cleanup in DocCommentParser to merge blockContent and inlineContent into a single method to parse "rich content" in a doc comment.
> 
> **Note:** This is dependent on PR #13362, to convert `DocCommentParser` to use enhanced switch.

Jonathan Gibbons has updated the pull request incrementally with one additional commit since the last revision:

  address review feedback

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Changes:
  - all: https://git.openjdk.org/jdk/pull/13431/files
  - new: https://git.openjdk.org/jdk/pull/13431/files/1ed86235..9d64e951

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13431&range=05
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13431&range=04-05

  Stats: 8 lines in 1 file changed: 0 ins; 4 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/13431.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13431/head:pull/13431

PR: https://git.openjdk.org/jdk/pull/13431