RFR: 8274308: Improve efficiency for HandshakeContext initialization.

[Clive Verghese]

Hi,

We have identified that the `HandshakeContext` initialization takes up a close 
to 50% of the flame graph for startHandshake. I have moved the computation of 
the `activeProtocols` and `activeCipherSuites` from the HandshakeContext 
constructor to SSLConfiguration class because the values used to compute the 
two list are available in the SSLConfiguration. 

In order to reuse this, I have initialized SSLConfiguration in the 
SSLSocketFactory and reused this when possible for Client Socket Constructors 
in the SSLSocketImpl. 

Sockets created from the SSLSocketFactory see this improvements. 

Old Benchmarks

Benchmark                                   Mode  Cnt  Score   Error   Units
SSLStartHandshake.handshakeBenchmark       thrpt   25  0.247 ± 0.011  ops/ms
SSLStartHandshake.handshakeBenchmark        avgt   25  4.210 ± 0.445   ms/op

New Benchmarks

SSLStartHandshake.handshakeBenchmark       thrpt   25  0.257 ± 0.017  ops/ms
SSLStartHandshake.handshakeBenchmark        avgt   25  3.967 ± 0.208   ms/op



I have also attached the JFR profiles from before and after the change.
Before
<img width="2325" alt="SSLOverhead-old" 
src="https://user-images.githubusercontent.com/934461/135705010-a8502966-c6be-4cb5-b743-4a5b382c8e1f.png";>

After 
<img width="2310" alt="SSLOverhead-new" 
src="https://user-images.githubusercontent.com/934461/135705007-ea852b36-e10f-4741-a166-249270b34465.png";>
 
We have been able to optimize the `TransportContext.kickstart` function by 
removing the `HandshakeContext.<init>`  initialization and reduce the time to 
start the handshake by reusing `activeProtocols` and `activeCipherSuites`

In addition to the SSL and http tests, I have run tier-1 and tier-2 tests and 
ensure that they pass. 

Looking for your feedback

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

Commit messages:
 - 8274308: Improve efficiency for HandshakeContext initialization
 - Benchmark

Changes: https://git.openjdk.java.net/jdk/pull/5793/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=5793&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8274308
  Stats: 796 lines in 8 files changed: 607 ins; 148 del; 41 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5793.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5793/head:pull/5793

PR: https://git.openjdk.java.net/jdk/pull/5793