Rollup merge of #134679 - ChrisDenton:rm-readonly, r=Mark-Simulacrum

Windows: remove readonly files

When calling `remove_file`, we shouldn't fail to delete readonly files. As the test makes clear, this make the Windows behaviour consistent with other platforms. This also makes us internally consistent with `remove_dir_all`.

try-job: x86_64-msvc-ext1

Author: Urgau