[EVPN][yang]VRF yang model doesn't contain vni field

[dgsudharsan]

Description

VRF yang model doesn't contain VNI field. The VNI field is required for EVPN configuration.
https://github.com/sonic-net/sonic-buildimage/blob/master/src/sonic-yang-models/yang-models/sonic-vrf.yang

The VRF table schema as per EVPN HLD is below
https://github.com/sonic-net/SONiC/blob/master/doc/vxlan/EVPN/EVPN_VXLAN_HLD.md

;Existing table
;defines virtual routing forward table. Updated to stores VNI associated with VRF
;
;Status: stable

key = VRF_TABLE:VRF_NAME ;
fallback = "true"/"false"
vni = 1*8DIGIT ; VNI associated with VRF

Steps to reproduce the issue:

Describe the results you received:

VRF table doesn't contain vni

Describe the results you expected:

VRF table should contain vni field

Output of show version:

(paste your output here)

Output of show techsupport:

(paste your output here or download and attach the file here )

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

[dgsudharsan]

@srj102 @adyeung @zhangyanzhao FYI

[adyeung]

@tapashdas to post VNI support in sonic-vrf.yang

[tapashdas]

ETA : 02/17

[zhangyanzhao]

PR was merged and close this issue.