RFR: JDK-8267219: Javadoc method summary breaks when {@inheritDoc} from an empty parent [v3]

[liach]

> This change fixes when a method body has only inline tags that produce no output, the method summary will get eaten.
> 
> This change allows `{@inheritDoc}` from empty parents to go through the code path used by `-nocomment` and properly generate tables.
> 
> All `jtreg:test/langtools/jdk/javadoc/doclet` tests pass.

liach has refreshed the contents of this pull request, and previous commits have been removed. The incremental views will show differences compared to the previous content of the PR. The pull request contains one new commit since the last revision:

  JDK-8267219: Javadoc method summary breaks when {@inheritDoc} from an empty parent

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/4066/files
  - new: https://git.openjdk.java.net/jdk/pull/4066/files/13d78642..6e4435cd

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=4066&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=4066&range=01-02

  Stats: 112 lines in 6 files changed: 40 ins; 59 del; 13 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4066.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4066/head:pull/4066

PR: https://git.openjdk.java.net/jdk/pull/4066