[browser][MT] pre-load threads early in dotnet.js

[pavelsavara]

• pre-load threads early in dotnet.js
  • they are merged into emscripten pool in new populateEmscriptenPool
• introduce new workerNumber sequence
  • send monoThreadInfo from UI to worker together with config
• introduce pthreadPoolReady config as floating pool and keep pthreadPoolSize as pre-init pool. See getNewWorker
• moved mono_wasm_init_diagnostics bit later, when thread pool is ready, but before mono start
• moved init_finalizer_thread even later, 200ms after runtime is ready. This may improve GC deadlock
• refactor how we handle emscripten internals, separated UI and workers
• move thread typescript types to types\internal.ts

[ghost]

Tagging subscribers to 'arch-wasm': @lewing
See info in area-owners.md if you want to be subscribed.

Issue Details

---

• pre-load threads early in dotnet.js
• refactor how we handle emscripten internals
• move thread typescript types

Author:	pavelsavara
Assignees:	-
Labels:	arch-wasm, area-System.Runtime.InteropServices.JavaScript, os-browser
Milestone:	9.0.0

[pavelsavara]

/azp run runtime-wasm

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[pavelsavara]

/azp run runtime-wasm

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).