fix #3317

fix #3336

Instead, generate a uuid for that message

From XEP 0045:
“Note: the requirement to reflect the 'id' attribute was added in version
1.31 of this XEP. Servers following the new specification SHOULD advertise
that with a disco info feature of 'http://jabber.org/protocol/muc#stable_id'
on both the service domain and on individual MUCs, so that clients can check
for support.”

fix #3283

Otherwise we can imagine that two clients changing this value at the same
time would mix things up.

ref #3275

fix #3275

This reverts commit 3f088e7b.

This reverts commit ba879a88.

This reverts commit d62ca9f8.

ref #3273

ref #3273

fix #3273

fix #3339

fix #3337

Because apparently the IDs are not always incrementing. We still use them to
know the order of two messages that were received at the same second (in
this case, the ID will always be incrementing).