feat: support config.enforce_ro(true|false)

  * This method is needed for autofailover mechanisms mainly to enforce
    read_only=true during loading phase of tarantool.

  Before this patch race condition existed between autofailover and
  moonlibs/config recovering behaviour.

  If master crashes but fastly restartes then it initiates long running
  loading phase. Master recovers as read_only=true but after returning
  from box.cfg moonlibs/config retrieves config from ETCD and rechecks
  read_only option.

  This lead to situation when autofailover may change ETCD configuration
  when master is about to leave loading phase but autofailover already
  confirmed that master is "loading".

  Having method config.enforce_ro it is now possible for external
  autofailover to firstly enforce_ro of loading master and then change
  ETCD configuration and promote other candidate fixing races and
  stabilizes FSM

config.lua

@@ -665,7 +665,7 @@ local function etcd_load( M, etcd_conf, local_cfg )
 					" with replication:"..table.concat(cfg.box.replication,", "),
 					string.format("timeout: %s, quorum: %s, lag: %s",
 						cfg.box.replication_connect_timeout
-							or ('def:%s'):format(load_cfg.default_cfg.replication_connect_quorum or 30),
+							or ('def:%s'):format(load_cfg.default_cfg.replication_connect_timeout or 30),
 						cfg.box.replication_connect_quorum or 'def:full',
 						cfg.box.replication_sync_lag
 							or ('def:%s'):format(load_cfg.default_cfg.replication_sync_lag or 10)
@@ -751,6 +751,7 @@ end
 ---@field public _load_cfg table
 ---@field public _flat table
 ---@field public _fencing_f? Fiber
+---@field public _enforced_ro? boolean
 ---@operator call(moonlibs.config.opts): moonlibs.config
 
 ---@type moonlibs.config
@@ -779,7 +780,20 @@ local M
 					return
 				end
 			end
-		end
+		end,
+		enforce_ro = function(enabler)
+			local previous = M._enforced_ro
+			if enabler == true then
+				M._enforced_ro = true
+			elseif enabler == false then
+				M._enforced_ro = false
+			end
+			return previous == M._enforced_ro, {
+				info_ro = box.info.ro,
+				cfg_ro = box.cfg.read_only,
+				_enforced_ro = M._enforced_ro,
+			}
+		end,
 	},{
 		---Reinitiates moonlibs.config
 		---@param args moonlibs.config.opts
@@ -1014,6 +1028,9 @@ local M
 						log.info("Reloading config after start")
 
 						local new_cfg = load_config()
+						if M._enforced_ro then
+							new_cfg.box.read_only = true
+						end
 						local diff_box = value_diff(cfg.box, new_cfg.box)
 
 						-- since load_config loads config also for reloading it removes non-dynamic options