Add RWF_ATOMIC constant to os module

[rruuaanng]

Feature or enhancement

Proposal:

This issue suggests adding new os constants.

fd = /* open a file */
buffers = [/* some bytes */]
os.pwritev(fd, buffers, 0, RWF_ATOMIC) # Either the write operation is successful, or nothing is written.

Has this already been discussed elsewhere?

No response given

Links to previous discussion of this feature:

No response

Linked PRs

• gh-127921: Add RWF_ATOMIC constant to os module #127922