feat: improve initialization with RAII patterns and runtime IDs

[adrian-niculescu]

This PR improves runtime initialization correctness and modernizes V8 API usage:

Context Management (RAII):
Adds Context::Scope RAII pattern to RunMainScript for proper context handling. The Context::Scope ensures the context is correctly exited when the scope ends, even if exceptions occur. This is the recommended V8 C++ API pattern per v8-locker.h documentation.

Note: Runtime::Init continues to use manual context->Enter() because the context must remain entered for the runtime's entire lifetime, not just during initialization.

Runtime ID Generation:
Introduces a static atomic counter (nextRuntimeId_) that generates unique IDs for each Runtime instance during initialization. This provides reliable runtime identification for both main and worker threads using thread-safe atomic operations with memory_order_relaxed (appropriate for ID generation).

The patterns align with modern C++ best practices and V8 API recommendations.

[adrian-niculescu]

Noticed the test failure now. On it.
L.E.: Fixed! Sorry, @NathanWalker! Reverted to context->Enter() in Runtime::Init- the context must outlive initialization. No matching Exit() needed; V8's isolate disposal handles cleanup.

[edusperoni]

The runtime ID change introduces a new bug where the main thread runtime is now considered a Worker. Also, you'll get duplicate runtime ids because the worker ids and runtime ids aren't generated from the same atomic int.

ios/NativeScript/runtime/Worker.mm

Line 127 in fd2703d

runtime->SetWorkerId(worker->WorkerId());

@NathanWalker please hold off merging until at least a proper review comes in.

I'm reverting this for now

[adrian-niculescu]

The runtime ID change introduces a new bug where the main thread runtime is now considered a Worker. Also, you'll get duplicate runtime ids because the worker ids and runtime ids aren't generated from the same atomic int.

ios/NativeScript/runtime/Worker.mm

Line 127 in fd2703d

runtime->SetWorkerId(worker->WorkerId());

@NathanWalker please hold off merging until at least a proper review comes in.

I'm reverting this for now

Will look into this and come back to you.

[adrian-niculescu]

The runtime ID change introduces a new bug where the main thread runtime is now considered a Worker. Also, you'll get duplicate runtime ids because the worker ids and runtime ids aren't generated from the same atomic int.

ios/NativeScript/runtime/Worker.mm

Line 127 in fd2703d

runtime->SetWorkerId(worker->WorkerId());

@NathanWalker please hold off merging until at least a proper review comes in.

I'm reverting this for now

@edusperoni, I apologize! You are right that the change is wrong in the current implementation due to IsRuntimeWorker() returning true for an id > 0.
I want to add that the change was not completely idiotic, just misplaced (should not have pushed it here): our fork that implemented support for ESM modules before you (you just recently did this in the 9.0.0 release) because we wanted to use dynamic imports; this was at a time when you didn't need this as bundling takes away the need for most situations where an import is needed. In our implementation the runtime id was used as a map key in the ESModule loader to ensure each runtime in the process gets its own one-time ESM setup. Sorry!