Add type restrictions to Log directory

[Vici37]

This is the output of compiling cr-source-typer and running it with the below incantation:

CRYSTAL_PATH="./src:lib" ./typify spec/all_spec.cr 
--error-trace 
--exclude src/crystal/ 
--stats --progress 
--ignore-private-defs 
--ignore-protected-defs 
--union-size-threshold 2 
--include-splats 
src/log

This is related to #15682 .