RFR: 8170305: URLConnection doesn't handle HTTP/1.1 1xx (informational) messages [v4]

[Jaikiran Pai]

> Can I please get a review of this change which proposes to fix https://bugs.openjdk.org/browse/JDK-8170305?
> 
> The commit in this PR changes the internal implementation of `HttpURLConnection` to ignore interim informational 1xx responses from server and continue to wait for the final response. This is a similar fix to what we did in the new `HttpClient` API in https://github.com/openjdk/jdk/pull/10169.
> 
> A new test has been added to use the `HttpURLConnection` to reproduce the issue and verify the fix.
> 
> tier1, tier2 and tier3 testing is in progress with this change.

Jaikiran Pai has updated the pull request incrementally with one additional commit since the last revision:

  fix test server to avoid hang in test

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/10229/files
  - new: https://git.openjdk.org/jdk/pull/10229/files/08e681b5..c4b62c5b

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=10229&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=10229&range=02-03

  Stats: 14 lines in 1 file changed: 7 ins; 3 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/10229.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10229/head:pull/10229

PR: https://git.openjdk.org/jdk/pull/10229