IR: Revise config and make it more convenient for administration

partially inspired by @532910 administration experience

we have neofs-ir app with its sample config file

within this i propose to make several config improvements

Defaults

define values that must always be set (usually these are network endpoints, keys, etc.). If a value can be set to default, which is applicable in most practical cases, then make the configuration optional.

it is also proposed to select the values from the configuration of which we want to free the administrator and make it static in the application (if any)

Sample config

describe the comments in the sample config in as much detail as possible for administrators to understand. For example, we can take consensus section

during the normal configuration process, the administrator only needs to explicitly set the required values. Optional values should be clear on the questions why?", for what? and what value?

Refs

see configuration for Ansible NeoFS IR role and in particular this section

Start with config/example/ir.yaml and the neofs-ir configuration entry points, then compare the settings with the referenced Ansible role defaults. Identify which values are required, which can have defaults, and which should be static, while expanding comments to explain optional settings. Done means the sample config clearly guides administrators through the required and optional values.