RFR: 8304818: Prune HttpURLConnection cache when corresponding Authenticator is garbage collected [v12]

[Michael McMahon]

> Hi,
> 
> Can I get a review for this please? This change uses a Cleaner to check when java.net.Authenticator instances become unreachable, and then prunes the authentication cache for entries that correspond to that Authenticator and therefore cannot be used again. This stops the authentication cache from growing in size unbounded. Note, this only happens in the probably unusual case where more than one Authenticator object is used. Normally there is no reason to use more than one instance.
> 
> Thanks,
> Michael.

Michael McMahon 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 19 additional commits since the last revision:

 - tests all passing now
 - tidy up
 - Merge branch 'master' into auth
 - update
 - update
 - Merge branch 'master' into auth
 - Update src/java.base/share/classes/sun/net/www/protocol/http/AuthCacheImpl.java
   
   Co-authored-by: Daniel Fuchs <67001856+dfuch at users.noreply.github.com>
 - error in test
 - Jai's review
 - update to remove dependency on AuthCacheImpl in j.n.Authenticator
 - ... and 9 more: https://git.openjdk.org/jdk/compare/3e009968...94b50c54

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/13159/files
  - new: https://git.openjdk.org/jdk/pull/13159/files/d2d27f8c..94b50c54

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13159&range=11
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13159&range=10-11

  Stats: 227713 lines in 1494 files changed: 213491 ins; 4312 del; 9910 mod
  Patch: https://git.openjdk.org/jdk/pull/13159.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13159/head:pull/13159

PR: https://git.openjdk.org/jdk/pull/13159