RFR: 8170305: URLConnection doesn't handle HTTP/1.1 1xx (informational) messages [v2]

[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 two additional commits since the last revision:

 - consider it a protocol violation if the server sends a 101 when the HttpURLConnection doesn't ask for a connection upgrade
 - 101 Upgrade isn't supported by HttpURLConnection, so ignore that response too

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/10229/files
  - new: https://git.openjdk.org/jdk/pull/10229/files/3576e619..0ede3681

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=10229&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=10229&range=00-01

  Stats: 30 lines in 2 files changed: 28 ins; 0 del; 2 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