RFR: JDK-8272374: doclint should report missing "body" comments [v2]

[Jonathan Gibbons]

> Please review a relatively simple update to have doclnt check for empty "descriptions" -- the body of a doc comment, before the block tags.
> 
> It is already the case that doclint checks for missing/empty descriptions in block tags, like @param, @return, etc.
> 
> There are three cases to consider:
> 
> * The comment itself is missing: this was already checked and reported as "missing comment".
> * The comment is present, but is empty ... this seems relatively unlikely, but is nevertheless checked and reported as "empty comment".
> * The comment is present but only has block tags. This is not always a problem, since the description may be inherited, for example, in an overriding method, but when it is an issue, it is reported as "no initial description". 
> 
> No diagnostic is reported if the description is missing but the first tag is `@deprecated`, because in this case, javadoc will use the body of the `@deprecated` tag for the summary. See [`Character.UnicodeBlock#SURROGATES_AREA`](https://docs.oracle.com/en/java/javase/15/docs/api/java.base/java/lang/Character.UnicodeBlock.html#SURROGATES_AREA) and the corresponding entry in the summary table to see an example of this situation.
> 
> Diagnostics are reported if the declaration is not an overriding method and does not begin with `@deprecated`.  This occurs in a number of places in the `java.desktop` module, often where the doc comment is of the form `/** @return _description_ */`.  To suppress those warnings for now, the `-missing` option is added to `DOCLINT_OPTIONS` for the `java.desktop` module.  To see the effects of this anti-pattern, look at the empty descriptions for [`javax.swing.text.html.parser.AttributeList`](https://docs.oracle.com/en/java/javase/15/docs/api/java.desktop/javax/swing/text/html/parser/AttributeList.html#method.summary)
> 
> Many of the doclint tests needed to be updated, because of their over-simplistic minimal comments. It was not possible, in general, to avoid updating the source code while preserving line numbers, so in many cases, the golden `*.out` files had to be updated as well.
> 
> A new test is added, focussing on the different forms of empty/missing descriptions, as described above.

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

  address review comment

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/5106/files
  - new: https://git.openjdk.java.net/jdk/pull/5106/files/60c6f569..6c875688

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=5106&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=5106&range=00-01

  Stats: 3 lines in 1 file changed: 0 ins; 1 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5106.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5106/head:pull/5106

PR: https://git.openjdk.java.net/jdk/pull/5106