Inspector: Track async stacks only when necessary

[ofrobots]

This is an alternative to #16260. It depends on a back port of an upstream fix (included), but solves the problem much more elegantly & comprehensively.

With this change, we do async stack tracking only when explicitly
requested by the inspector client. This avoids unnecessary overhead
for clients that might not be interested in async stack traces.

In practical terms, this means that we still get async stack tracking right from startup when --inspect-brk is used for debuggers that enable async stacks (DevTools does this by default, and I think WebStorm and others as well).

When using --inspect, we no longer enable async stack tracking by default. The inspector client can request async stack tracking at the time of the connection. Any async resources already created will not have stack tracking. I believe this is the right behavior (see #16180). Users needing async stack tracking right from startup can use --inspect-brk.

Fixes: #16180

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• commit message follows commit guidelines

Affected core subsystem(s)

deps:v8, inspector

/cc @nodejs/v8-inspector
CI: https://ci.nodejs.org/job/node-test-pull-request/10836/https://ci.nodejs.org/job/node-test-pull-request/10862/https://ci.nodejs.org/job/node-test-pull-request/10865/https://ci.nodejs.org/job/node-test-pull-request/11030/
V8-CI: https://ci.nodejs.org/view/All/job/node-test-commit-v8-linux/1000/https://ci.nodejs.org/view/All/job/node-test-commit-v8-linux/1001/

[ofrobots]

@nodejs/v8 PTAL as well. The back port adds a vtable entry. This should be ABI compatible by virtue of being the last virtual function.

[targos]

Now that V8 6.2 has landed, we can update the embedder string instead.

[ofrobots]

Done.

[ofrobots]

Looking at the CI, the added test crashes on Windows VS2017. There is suspicion that it might be related to #15558.

[refack]

Stressing
built with VS2017: https://ci.nodejs.org/job/node-stress-single-test/1458/nodes=win2012r2-mp-vs2017/
built with VS2015: https://ci.nodejs.org/job/node-stress-single-test/1459/nodes=win2012r2-mp-vs2015/

[ofrobots]

Curiously, in the stress test it didn't fail at all. I can reproduce this with ~50% intermittency on a vs2017 build on a local windows machine. I am fairly confident that this is related to #15558. Getting rid of the session.disconnect from the test makes it pass reliably.

[refack]

Stress on Windows2008 gives 64% fails - https://ci.nodejs.org/job/node-stress-single-test/1460/nodes=win2008r2-mp-vs2017/console

[ofrobots]

I have disabled part of the test affected by flakiness from #15558. New CI: https://ci.nodejs.org/job/node-test-pull-request/10865/

[bnoordhuis]

Four space indent (line continuation.)

[ofrobots]

Done.