tmpfs: Expose filesystem features via sysfs

Expose filesystem features through sysfs, so userspace can query if
tmpfs support casefold.

This follows the same setup as defined by ext4 and f2fs to expose
casefold support to userspace.

Signed-off-by: André Almeida <andrealmeid@igalia.com>
Link: https://lore.kernel.org/r/20241021-tonyk-tmpfs-v8-8-f443d5814194@igalia.com


Reviewed-by: Gabriel Krisman Bertazi <krisman@suse.de>
Signed-off-by: Christian Brauner <brauner@kernel.org>