8180044: java/net/httpclient/ManyRequests.java failed due to timeout
Summary: Fixes several race conditions observed while testing.
Reviewed-by: michaelm, msheppar, prappo

8178147: Race conditions in timeout handling code in http/2 incubator client
Summary: Timeout handling code (in particular cancel(IOException)) is modified to take into account cancellation arising before exchange implementation is established or response completable future is created. TimeoutEvent::compareTo method is modified to be consistent with TimeoutEvent::equals.
Reviewed-by: prappo, chegar, michaelm

8164625: Pooled HttpConnection should be removed during close
Reviewed-by: dfuchs, michaelm

8175274: Fix httpclient asynchronous usage
Reviewed-by: dfuchs, michaelm

8170648: Move java.net.http package out of Java SE to incubator namespace
Reviewed-by: chegar, dfuchs, michaelm, prappo, skuksenko
Contributed-by: Chris Hegarty <chris.hegarty@oracle.com>, Daniel Fuchs <daniel.fuchs@oracle.com>, Michael McMahon <michael.x.mcmahon@oracle.com>, Pavel Rappo <pavel.rappo@oracle.com>, Sergey Kuksenko <sergey.kuksenko@oracle.com>, anthony.vanelverdinghe@gmail.com