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

[Jonathan Gibbons]

On Wed, 19 Apr 2023 15:45:57 GMT, Jonathan Gibbons <jjg at openjdk.org> wrote:

>> Yes, will change, for clarification and to better distinguish it from the description for PREAMBLE
>
> Or no.   As a phase, it is the part between the PREAMBLE and POSTAMBLE. It is when reading the main description, and rich-text content of block tags, in both cases excluding the content of inline tags, which are read with INLINE phase.
> 
> I'll definitely have to work on this text.

Functionally, `BODY` is unchanged. The only change to `Phase` is to add `INLINE` -- as well as trying to document it all.

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PR Review Comment: https://git.openjdk.org/jdk/pull/13431#discussion_r1171590092