code_size: run report and diff on Windows (#4086)

`tools/code_size.py report` and `diff` run on native Windows with `python -X utf8`: '/' size keys and drive-less, case-insensitive filters, linker scripts read through ninja's cmd.exe wrapper, CMake-shortened objects keyed through build.ninja, and a timeout stops the whole command tree with taskkill. ESP-IDF, snapshot/compare and paths with spaces are not supported there; CI stays Linux-only.