Hello, welcome to the community! And thanks for reporting this strange behavior.
I did not manage to reproduce it with recent versions of SonarLint, but I created a ticket to investigate and see if we can prevent this accumulation of temporary directories.
We are happy to let you know that the mentioned ticket is now closed and the latest version of SonarLint for VSCode (3.21.0) includes the fix to this issue. Thank you for your continued feedback