introduce new CLI options for conf module

[TarantoolBot]

There are two new options introduced in Tarantool CLI:

• --name (-n) to specify instance name to be started. The option can be
  omitted in case TT_INSTANCE_NAME environment variable is set.
• --config (-c) to specify the path to the config file. If the option
  is not set the value of TT_CONFIG environment variable is considered.
  Requested by @igormunkin in tarantool/tarantool@9db7d6c.

[andreyaksenov]

See also: #2364, #2021

[andreyaksenov]

https://docs.d.tarantool.io/en/doc/3.0/concepts/configuration/#command-line-options