Update documentation for AFT Limited Prefix Streaming and aft-summaries behavior

[romeyod]

AFT global-filter was introduced openconfig/public#1441 and the initial testing READMEs were added in openconfig/featureprofiles#5217.

My understanding is that aft-summaries should reflect the total AFT entries in the HW FIB, not the filtered summary. Specifically, the Route Summary (per protocol route count in the FIB) should remain untouched, meaning it will still contain the counts related to all prefixes.
The YANG paths in question are:
/network-instances/network-instance[name]/afts/aft-summaries/ipv4-unicast/protocols/protocol[origin-protocol]/state/counters/aft-entries
/network-instances/network-instance[name]/afts/aft-summaries/ipv6-unicast/protocols/protocol[origin-protocol]/state/counters/aft-entries

To ensure this expected behavior is clear, we need to document this expectation directly in the public YANG model descriptions.

[dplore]

This is also my understanding. If a filtered number was needed, a new leaf could be introduced.

@navaneethyv for comment

[romeyod]

@ElodinLaarz since AFT global-filter was introduced by @ElodinLaarz

[ElodinLaarz]

Yes, the filter only is defined to only affect the subtrees /network-instances/network-instance/afts/ipv[46]-unicast/...

@paramasivamn1 -- (maybe not active in this repo...) is the new owner of the feature, though, if we wanted to follow-up. (reviewed openconfig/featureprofiles#5217)