RFR: 8308185: Update Http2TestServerConnection to use SSLSocket.startHandshake()

[Jaikiran Pai]

Can I please get a review of this change in the `jdk.httpclient.test.lib.http2.Http2TestServerConnection` which proposes to use the `SSLSocket.startHandshake()`  to API propogate any handshake exception back to the test that uses this test server?

This addresses https://bugs.openjdk.org/browse/JDK-8308185 and as noted in that JBS issue should help diagnoze any handshake failures in httpclient tests, a bit more easily.

tier2 testing with this change came back without any failures.

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Commit messages:
 - 8308185: Update Http2TestServerConnection to use SSLSocket.startHandshake()

Changes: https://git.openjdk.org/jdk/pull/14012/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=14012&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8308185
  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/14012.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14012/head:pull/14012

PR: https://git.openjdk.org/jdk/pull/14012