Inspect API support for top-level targetRef `sectionName`

[lobkovilya]

Description

With the new design it'll be possible select a single inbound port for configuration. Once #12375 is implemented we should be able to update the Inspect API to reflect the fact only a single port is configured by the policy.

Today "fromRules" already has an inbound object we need to check if sectionName works out-of-the-box or requires additional support.