Example:

```console
tarantool> picolib.whoami()
---
- raft_id: 1
  cluster_id: demo
  instance_id: i1
...

tarantool> picolib.peer_info("i1")
---
- raft_id: 1
  instance_id: i1
  instance_uuid: 68d4a766-4144-3248-aeb4-e212356716e4
  replicaset_uuid: e0df68c5-e7f9-395f-86b3-30ad9e1b7b07
  replicaset_id: r1
  advertise_address: localhost:3301
  target_grade: Online
  current_grade: Online
...
```

1. Encapsulate topology access in a dedicated function.
2. Remove obsolete CachedCell

`KVCell` contains an optional value and provides access by key in two
flavors:

```rust
fn take_or_drop(&mut self, key: &K) -> Option<T>
fn take_or_keep(&mut self, key: &K) -> Option<T>
```

Both return `Some` value only if provided key matches the contained one.

The behavior differs when the provided key doesn't match:
- `take_or_drop` always leaves the cell empty. It supersedes
  `CachedCell` and copies its behavior.
- `take_or_keep` retains contained value. It's a replacement for
  `JointStateLatch`.

Georgy Moshkin authored 2 years ago and Georgy Moshkin committed 2 years ago

replication_factor now goes into cluster_state

To highlight all the logging messages containing the given key do this:
* rust: `tlog::highlight_key(log_key, Some(color))`.
* lua: `picolib.log.highlight_key(log_key, color)`.

To disable highlight for the given key do this:
* rust: `tlog::highlight_key(log_key, None)`.
* lua: `picolib.log.highlight_key(log_key)`.

To disable highlighting of all keys do this:
* rust: `tlog::clear_highlight()`.
* lua: `picolib.log.clear_highlight()`.