Add v2r mapping for Switch Packet Integrity Drop counter

[SuvarnaMeenakshi]

Why I did it

Add v2r mapping to get SAI_SWITCH_STAT_PACKET_INTEGRITY_DROP counters for Chassis platform.

How I did it

Read COUNTERS_DEBUG_NAME_SWITCH_STAT_MAP to get OID and map to Counters so that telemetry can use "COUNTERS/SWITCH*" or "COUNTERS/SWITCH_ID" or "COUNTERS/SWITCH_ID-asic0" to get packet integrity drop counters.

How to verify it

Add unit-test:

    --- PASS: TestGnmiGet/get_COUNTERS:SWITCH_ID (0.00s)
    --- PASS: TestGnmiGet/get_COUNTERS:SWITCH_ID* (0.00s)
    --- PASS: TestGnmiGet/Invalid_fabric_port_key_getSWITCH_ID- (0.00s)
    --- PASS: TestGnmiGetMultiNs/get_COUNTERS:SWITCH_ID-asic0 (0.00s)
    --- PASS: TestGnmiGetMultiNs/get_COUNTERS:SWITCH_ID* (0.00s)
    --- PASS: TestGnmiGetMultiNs/Invalid_fabric_port_key_getSWITCH_ID (0.00s)

Verify on Chassis:

gnmi_get -target_addr localhost:50051 -xpath "COUNTERS/SWITCH*"  -xpath_target COUNTERS_DB -insecure 
COUNTERS/SWITCH*: [{"SWITCH_ID-asic0": {'SAI_SWITCH_STAT_PACKET_INTEGRITY_DROP': '0'}, {"SWITCH_ID-asic1": {'SAI_SWITCH_STAT_PACKET_INTEGRITY_DROP': '0'}} 

Which release branch to backport (provide reason below if selected)

• 201811
• 201911
• 202006
• 202012
• 202106
• 202111

Description for the changelog

Link to config_db schema for YANG module changes

A picture of a cute animal (not mandatory but encouraged)

[mssonicbld]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[vmittal-msft]

Using PR - #423 to port these changes.