[yang] Need Yang for TUNNEL table

[ganglyu]

Description

We don't have Yang model for TUNNEL table.

Steps to reproduce the issue:

1. Run build pipeline for below PR:
   [sonic-cfggen] Track missing yang models #10963
2. Check build log:
   sonic_yang(6):Note: Below table(s) have no YANG models: PEER_SWITCH, VOQ_INBAND_INTERFACE, CONSOLE_PORT, TUNNEL, MUX_CABLE, DEVICE_NEIGHBOR_METADATA, DHCP_SERVER, RESTAPI, CONSOLE_SWITCH

Describe the results you received:

sonic-config-engine unit test failed.

Describe the results you expected:

sonic-config-engine unit test should pass.

Output of show version:

(paste your output here)

Output of show techsupport:

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Additional information you deem important (e.g. issue happens only occasionally):

[zhangyanzhao]

MSFT will handle this

[zhangyanzhao]

@prsunny can you please help to create the YANG model for this table? Thanks.