embedded metrics configuration

[TarantoolBot]

Related dev. issue(s): tarantool/tarantool#7725

Product: Tarantool
Since: 3.0
Root document:

• [Config] Configuration reference (YAML) #3664
• https://www.tarantool.io/en/doc/latest/reference/configuration/
• https://www.tarantool.io/en/doc/latest/book/monitoring/api_reference/#lua-function.metrics.cfg

SME: @ DifferentialOrange

Details

This patch add new box.cfg dynamic parameter: metrics. It is a table
with the same effect as in metrics.cfg. metrics.cfg has its own
documentation, see [1].

1. https://www.tarantool.io/en/doc/latest/book/monitoring/api_reference/#lua-function.metrics.cfg
   Requested by @ DifferentialOrange in tarantool/tarantool@8f95eaa.