Hello,
I have exactly the same problem. The file named "Photos Library.photoslibrary" appears in the Bin all the time. I empty the Bin, and after a little while it is back. And it grows slowly, starting with a few MBytes and becomes several GBytes big after a while. Once, I just let it grow and it got to more than 70 GByte, despite that my Photos Library in ~/Pictures is around 50 GBytes.
This has never happened with previous versions of MacOS. This funny behaviour started when I upgraded to Monterey. I now run 12.0.1.
I have not been able to find a solution to this problem, just people answering "It is in the Bin because you put it there". That is not the case. It ends up in the Bin because there must be a bug in the Monterey OS.
My Photos Library in ~/Pictures is still intact, so this is not catastrophic, just annoying.
Cheers,
Geir