fs_event: enable bit operations for the uvw_fs_event enum

[fcelda]

This PR adds the UVW_ENUM member to the enum class uvw_fs_event to enables the bitwise operations over the type.

The libuv documentation says that the flags are a bit mask:

The events parameter is an ORed mask of uv_fs_event elements.

-- https://docs.libuv.org/en/v1.x/fs_event.html#c.uv_fs_event_cb:

[skypjack]

I fixed the issue with the thread class. Can you rebase on main and rerun the tests for a double check? Thanks. 🙏