(future) ESR115 & better JS profiling

[wraitii]

Good news and bad news about the future.

As of Firefox 115, which will be the latest ESR soon, I can finally properly profile the game including JIT code.
The only thing to do is compile spidermonkey with `enable-perf` and `--enable-jitspew` (I think), then run it form within https://github.com/mstange/samply like so: `IONPERF=func PERF_SPEW_DIR=. samply record -n --rate 10000 binaries/system/pyrogenesis -mod=public -autostart="random/continent"  --autostart-ai="1:petra" -autostart-ai="2:petra" -autostart-nonvisual -autostart-seed=150`

This gives you a full profile that you can then access on the firefox profiler, like so: https://share.firefox.dev/3IHH7ho (AI 1v1)
There are some interesting overall insights:

• In this AI 1v1 75-80% of the time is spent in C++ code. But a lot of that time is calls from JS.
• As I have reported in the staff forums in the past, the main cost in the SimUpdate is `Timer Update` (about 15% of total time), split between ResourceGatherer, ProductionQueue, Builder, Attack, DelayedDamage. 
• Most of the code appears to end up properly jitted.
• But the GCs 'dump' the JIT code regularly, which means we spend more time in baseline than we probably should. I have reported a bug about this, we'll see what happens: https://bugzilla.mozilla.org/show_bug.cgi?id=1834848
• There is a fair amount of Spidermonkey overhead, though there are things we could improve.
  • To take the Example of calling `Engine.QueryInterface`, the costs breakdown as follow:
    • ToJSVal<IComponent*> is about 40-45%. This is largely because of D5004.
    • The actual C++ QueryInterface is only 20%, which is slow because of std::map. But it's not the most major cost.
    • Getting the ComponentManager pointer is 7%
    • ScriptRequest enters the realm (for no reason), which accounts for about 10% total
  • So as you can see there are a lot of things we could do to skip some time, but it's also going to be kinda hard.

Some obvious things that show up and could probably be improved:

• Having a `Engine.QueryInterfaces()` function is probably interesting.
• Identity:Init() is slow because of splitting the identity classes. We can cache that in ParamNode directly I think.
• There are some regex constructions in loop which are slow, such as in MatchesClassList
• AI Interface and AI Proxy are fairly slow.
• The AI in general also seems poorly jitted, and that might have to do with how the objects are structured, hard to say.
• Modifiers are kinda costly, but we knew that.

Now, right now we are still on ESR92, so this is some ways off, but I have compiled it on a local branch, and I think the results are rather interesting, and encouraging for the future.

[Stan`]

@Bellaz89