[2.3.0] Checkmk Werk 16806 created: Handle unexpected files in 'cmk_addons/plugins'

[//]: # (werk v2) # Handle unexpected files in 'cmk_addons/plugins' key | value ---------- | --- date | 2024-04-23T12:04:08+00:00 version | 2.3.0b6 class | fix edition | cre component | checks level | 1 compatible | yes Checkmk 2.3.0 beta crashed during various operations if unexpected files where put into `local/lib/python3/cmk_addons/plugins/` or `local/lib/python3/cmk/plugins/`. They are ignored now.