feat(Interpreter): Improve interpreter event loop liveness for timers

[jeremylcarter]

Summary

• Ref-count timers to keep the interpreter event loop alive by default and release on cancel/finish.
• Switch the event loop to a blocking callback queue with SynchronizationContext dispatch for lower idle CPU and correct main-thread callbacks.
• Add interpreted-only tests for timer keep-alive and unref() exit behavior.

Testing

File: web-server.ts
Test: loadtest http://localhost:3000
Results:

Updated interpreter (SharpTS)

Target URL:          http://localhost:3000
Max time (s):        10
Concurrent clients:  80
Running on cores:    8
Agent:               none

Completed requests:  62251
Total errors:        0
Total time:          10.028 s
Mean latency:        12.3 ms
Effective rps:       6208

Previous interpreter (SharpTS)

Target URL:          http://localhost:3000
Max time (s):        10
Concurrent clients:  80
Running on cores:    8
Agent:               none

Completed requests:  6560
Total errors:        0
Total time:          10.05 s
Mean latency:        120.9 ms
Effective rps:       653

NodeJS - web-server.ts

Target URL:          http://localhost:3000
Max time (s):        10
Concurrent clients:  80
Running on cores:    8
Agent:               none

Completed requests:  19526
Total errors:        1127
Total time:          10.036 s
Mean latency:        40.2 ms
Effective rps:       1946

[nickna]

Nice. This is clever and effective.