Enforces E501 across almost all `pmb/` and `test/` files

This PR enforces PEP-8 E501 (Max line length of 79 characters) as asked in #1986 (closed) .Changes All lines that break this rule in pmb and test directories and changes static_code_analysis.sh to treat files that don't follow this as an exception. Replaces many string concatenations for f-strings where applicable.

Some files in pmb/aportgen/ have long multiline strings representing sh commands, and since I don't fully comprehend what those commands are doing I did not change anything inside those strings, adding them as exceptions to the flake8 check running at the end.

I feel that even if merged this does not fully closes - #1986 (closed), but it does go a long way towards it.