Add `getscriptfromthread` function

[samerop]

Add the getscriptfromthread function to sUNC
Some information on it from Zenith documentation:

[RazAPIx64]

Name 1 use case

[samerop]

Name 1 use case

It can identify which LocalScript fires a specific RemoteEvent or RBXScriptConnection

[Anbubu1]

Name 1 use case

helps to filter out threads returned by getreg