RFR: JDK-8290126: Add a check in JavadocTester for "javadoc should not crash" [v6]

[Jonathan Gibbons]

> Please review a simple update to `JavadocTester` to provide a default-on check that no stack traces were written to the STDERR stream.
> 
> There are also some minor cleanup edits suggested by the IDE.

Jonathan Gibbons 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 eight additional commits since the last revision:

 - fix broken test
 - Merge remote-tracking branch 'upstream/master' into 8290126.javadoctester-checkCrash
 - improve check in JavadocTester
   remove obsolete/now-broken check from DocTest.java
 - Merge remote-tracking branch 'upstream/master' into 8290126.javadoctester-checkCrash
 - Merge remote-tracking branch 'upstream/master' into 8290126.javadoctester-checkCrash
 - revert (defer) improvement of TagletManager error message; fix TestTFMBuilder.java
 - Respond to review feedback; add new test
 - JDK-8290126: Add a check in JavadocTester for "javadoc should not crash"

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Changes:
  - all: https://git.openjdk.org/jdk/pull/9458/files
  - new: https://git.openjdk.org/jdk/pull/9458/files/0b22f653..24be548e

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=9458&range=05
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=9458&range=04-05

  Stats: 64866 lines in 1037 files changed: 27976 ins; 30401 del; 6489 mod
  Patch: https://git.openjdk.org/jdk/pull/9458.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9458/head:pull/9458

PR: https://git.openjdk.org/jdk/pull/9458