ipintutil to get address data for a ns in bulk and process efficiently

[peteranish]

Summary/Description
The show commands "show ip interface" and "show ipv6 interface" consumes high cpu for a prelonged time period (200-300s for 4K interfaces). These show commands internally uses ipintutil for these show commands. This tool used python netifaces calls for each interface to populate the interface details. This lead to .06s time delay per interface leading to the showness in show output inaddition to high cpu utilization.
Type of change
The fix now gets the complete namespace addressing database on a single call from system and then populate the show database in a single parse. This reduces the overall time duration from >300s to <2s.
Approach
Do bulk processing
What is the motivation for this PR?
Performance improvement
How did you do it?
How did you verify/test it?
Show command executions before and after along with UT. PTF suite run.
Any platform specific information?
None

[mssonicbld]

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