[vnetorch] Prevent route deletion in default VRF upon conflicting route creation in non default VNET

[anish-n]

What I did
Modified vnetorch to not delete conflicting route space in default vrf if the vnet scope is non default

Why I did it
To support conflicting IP spaces

How I verified it
SWSS UT which shows that conflicting IP space is no longer deleted, and manual testing on device which shows this as well

Details if related
ASIC DB route deleteion issue can be seen below(which is fixed by this PR):
Route entry on switch:

B>*0.0.0.0/0 [20/0] via 10.0.0.57, PortChannel101, 03:33:15
  *                 via 10.0.0.59, PortChannel102, 03:33:15
  *                 via 10.0.0.61, PortChannel103, 03:33:15
  *                 via 10.0.0.63, PortChannel104, 03:33:15

Route entry in ASIC DB:

 127.0.0.1:6379[1]> hgetall "ASIC_STATE:SAI_OBJECT_TYPE_ROUTE_ENTRY:{\"dest\":\"0.0.0.0/0\",\"switch_id\":\"oid:0x21000000000000\",\"vr\":\"oid:0x3000000000026\"}"
1) "SAI_ROUTE_ENTRY_ATTR_PACKET_ACTION"
2) "SAI_PACKET_ACTION_FORWARD"
3) "SAI_ROUTE_ENTRY_ATTR_NEXT_HOP_ID"
4) "oid:0x5000000000677"

Add conflicting route entry in VNET:

vnet name    prefix         endpoint    mac address          vni  status
-----------  -------------  ----------  -----------------  -----  --------
Vnet1000     0.0.0.0/0      70.60.0.5   00:00:00:00:03:04  25000  active

Default route is deleted from default VRF:

127.0.0.1:6379[1]> hgetall "ASIC_STATE:SAI_OBJECT_TYPE_ROUTE_ENTRY:{\"dest\":\"0.0.0.0/0\",\"switch_id\":\"oid:0x21000000000000\",\"vr\":\"oid:0x3000000000026\"}"
1) "SAI_ROUTE_ENTRY_ATTR_PACKET_ACTION"
2) "SAI_PACKET_ACTION_DROP"
3) "SAI_ROUTE_ENTRY_ATTR_NEXT_HOP_ID"
4) "oid:0x0"

[mssonicbld]

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Pull request overview

This PR fixes a bug where routes in the default VRF were incorrectly deleted when conflicting routes were created in non-default VNETs. The fix modifies isRouteExists() to check for route existence in a specific VRF rather than always checking the default VRF.

• Modified isRouteExists() to accept a vrf_id parameter for VRF-specific route lookups
• Fixed return value in isRouteExists() from true to false when route table doesn't exist
• Updated all call sites in vnetorch to pass the appropriate VRF ID

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
orchagent/routeorch.h	Updated function signature to accept VRF ID parameter
orchagent/routeorch.cpp	Modified isRouteExists() to check routes in specified VRF and fixed return value when route table not found
orchagent/vnetorch.cpp	Updated three call sites to pass VRF ID to isRouteExists()
tests/vnet_lib.py	Added helper functions to verify default VRF routes and VNET route deletion, but contains bugs
tests/test_vnet2.py	Added new test and updated existing tests to validate conflicting route behavior with non-default VNETs

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