py3: use str literal instead of bytes literal

typing: fix type annotation

cffi: pass bytes instead of str to ffi.new("char[]", …) The type annotations seem to imply that the passed values are always already bytes, but they aren’t necessarily. Before Python 3.11, the documentation stated that bytes can be used to annotate arguments whose type is actually any of bytes, bytearray, or memoryview.

cffi: call bytes() instead of str() on CFFI buffer instances

cffi: pass C type and attribute names as str instead of bytes

py3: fix type of some elements of __all__ lists

copytracing: fix a bug in an edge case in metadata.compute_all_files_changes

rhg: ignore readonly FS error when saving dirstate The error is already ignored when the .hg directory is read-only, so this is only fair. (the python hg is silent on readonly fs, too)