When the reader is currently paused, it is resumed, fast-forwarded, then
paused again. The fast forwarding part can throw and this will lead to
destroying the reader without it being closed first.
Add a try-catch surrounding this part in the code. Also mark
`maybe_pause()` and `do_pause()` as noexcept, to make it clear why
that part doesn't need to be in the try-catch.
Fixes: #16606Closesscylladb/scylladb#16630
204d3284fa