tracing: etw/perf/lttng/etc multi-isolate support

[bnoordhuis]

Continuing from nodejs/help#1031: src/node_counters.cc and its ilk need to have their initialization split out into a per-isolate and per-context step for embedding to work with them. Some thoughts:

1. node.js won't know if initialization already happened if the isolate is created by the embedder, unless extra bookkeeping is added. Could hang off MultiIsolatePlatform::RegisterIsolate() - or could it?

2. the tracing code itself isn't multi-isolate ready in the slightest, it's all globals that need to move to IsolateData and Environment

3. some tracing flavors have (possibly inevitable) process-global state that should be protected by a uv_once_t or node::Mutex.

[Let0s]

I think this line and next one (which set callbacks to isolate) should not depends on Environment (embedder can create one isolate and set it for every Environment, that will be created). IMHO, adding callbacks should be somewhere in NodePlatform class, when it registers isolate.

[Trott]

@bnoordhuis This should remain open, yes? If so, is there someone particularly well-suited to try to move it forward? @nodejs/embedders maybe?

[bnoordhuis]

Yes, it's still an issue. I don't have suggestions for volunteers but they're more than welcome.

[bnoordhuis]

I think this issue has become obsolete after the removal of dtrace and etw in #43652 (and lttng and perfctr back in 2018.) I'll go ahead and close it.