Arista EOS, use sysObjectID for detection (to include vEOS) (#13534)

Also, simplify regex

includes/definitions/arista_eos.yaml

@@ -9,8 +9,7 @@ over:
     - { graph: device_mempool, text: 'Memory Usage' }
 discovery:
     -
-        sysDescr:
-            - Arista Networks EOS
+        sysObjectID: .1.3.6.1.4.1.30065.1
 poller_modules:
     wireless: false
     ipmi: false

includes/definitions/discovery/arista_eos.yaml

@@ -1,4 +1,4 @@
 modules:
     os:
-        sysDescr_regex: '/.+ version (?<version>.+) running on .+ (?<hardware>\S+)$/'
+        sysDescr_regex: '/ version (?<version>.+) running on .+ (?<hardware>\S+)$/'
         serial: ENTITY-MIB::entPhysicalSerialNum.1