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

[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.

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Commit messages:
 - 8170305: URLConnection doesn't handle HTTP/1.1 1xx (informational) messages

Changes: https://git.openjdk.org/jdk/pull/10229/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10229&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8170305
  Stats: 208 lines in 2 files changed: 207 ins; 0 del; 1 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