replication: introduce instance name

The instance name is carried with instance UUID everywhere in the
replication protocols. It is visible in all other instances via
_cluster and is displayed in monitoring.

Part of #5029

@TarantoolBot document
Title: `box.cfg.instance_name` and `box.info.name`
The new option `box.cfg.instance_name` allows to assign the
instance name to a human-readable text value to be displayed in
the new info key - `box.info.name`. Instances can see names of
their peers in `box.info.replication[id].name`.

The name is broadcasted in "box.id" built-in event as
"instance_name" key. It is string when set and nil when not set.

When set, it has to be unique in the instance's replicaset.

If a name wasn't set on cluster bootstrap (was forgotten or the
cluster is upgraded from a version < 3.0), then it can be set
on an already running instance via `box.cfg.instance_name`.

To change or drop an already installed name one has to use
`box.cfg.force_recovery == true` in all instances of the cluster.
After the name is updated and all the instances synced, the
`force_recovery` can be set back to `false`.

The name can be <= 63 symbols long, can consist only of chars
['0'-'9'], '-' and 'a'-'z'. It must start with a letter. When
upper-case letters are used in `box.cfg`, they are automatically
converted to lower-case. The names are host- and DNS-friendly.