mgr/rest: Trim request array and limit size

mgr/rest: Trim request array and limit size

Presently, the requests array in the REST module has the potential to grow
indefinitely, leading to excessive memory consumption, particularly when
dealing with lengthy and intricate request results.

To address this issue, a limit will be imposed on the requests array within
the REST module.
This limitation will be governed by the `mgr/restful/x/max_requests` configuration
parameter specific to the REST module.
when submit_request called we will check request array if exceed max_request option
if it does we will check if the future trimmed request finished and log error
message in case we are trimming un-finished requests.

Fixes: https://tracker.ceph.com/issues/59580
Signed-off-by: Nitzan Mordechai <nmordech@redhat.com>