chore: thread and thread manager into separate file

[myandrienko]

Just splitting a large file in two for easier navigation.

Also, removed throttling from throttledHandleConnectionRecovery here, mostly to avoid imports, but also because it's not a correct way to deal with this async method. More fixes to this method are coming in further PRs.

[github-actions]

Size Change: -1.93 kB (-0.45%)

Total Size: 426 kB

Filename	Size	Change
dist/browser.es.js	92.7 kB	-502 B (-0.54%)
dist/browser.full-bundle.min.js	52.8 kB	+109 B (+0.21%)
dist/browser.js	93.8 kB	-524 B (-0.56%)
dist/index.es.js	92.7 kB	-496 B (-0.53%)
dist/index.js	93.8 kB	-517 B (-0.55%)

_{compressed-size-action}