doc: tls: clarify server cipher list

* Make it clear that ECDHE-RSA-AES128-SHA256 and AES128-GCM-SHA256 are
  TLS v1.2 ciphers.

* Note that RC4 is under suspicion.
doc: tls: note that SSLv2 is disabled by default

As of commit 39aa894, SSLv2 support is disabled by default.  Update
the documentation to reflect that.
lib: introduce `.setMaxSendFragment(size)`

fix #6889
test: ignore tests when built without OpenSSL CLI

fix #6880
test: refactor to use common testcfg
test: move debugger repl into own section
debug client: connect after child is ready

We now wait to connect to the debuggee until we know that
its error stream has data, to ensure that the output message
"connecting..... ok" appears after "Debugger listening on port xyz"

I also increased the test timeout to let the more complex
tests finish in time on Windows

This change fixes the following unit tests on Windows:
 test-debugger-repl.js test-debugger-repl-term.js test-debugger-repl-utf8.js
 test-debugger-repl-restart.js
test: debug-signal-cluster increase timeouts

The test needs a little more time to run so that it passes for all
builds (eg: Windows, debug)
test: relax timing in test-http-exit-delay

This test was originally intended to guard against regressions for
commit 16b59cbc74c8fe2f8b30f3af4c2f885b7bfb6030.

As such, it only needs to ensure that process exit has not been held up
by the date cache timer, which would fire on the next second.
crypto: remove most of the `node_isolate` uses

All C++ code should be using `args.GetIsolate()` or `env->isolate()`.
Using static `node_isolate` var limits possible future functionality
(like multi-isolate support).