Fix: fix arista eos miscategorized as cisco ios

[mstopa-splunk]

In #2139 it has been reported that some Arista EOS logs are miscategorized as Cisco IOS.

In fact those two vendors use a very similar log format.
The difference is Arista will always contain program name before the first colon:
Aug 18 03:36:42 AleL3Agent-primary: %AGENT-6-INITIALIZED: Agent 'AleL3Agent-primary' initialized; pid=XXXX

In Cisco there is usually just a timestamp:
Feb 14 09:40:10.326: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/1, changed state to up

Sometimes timestamp with timezone:
{{ mark }}: {{ year }} {{ bsd }} PDT: %DAEMON-3-SYSTEM_MSG: ftp disabled, removing - xinetd[4930] {{ host }}

And sometimes also program name, but with all letters uppercase:
'{{ mark }}{{ bsd }} SYSMGR[919]: %Viptela-{{ host }}-sysmgrd-6-INFO-1400002: Notification: 3/17/2022 18:35:12 system-login-change severity-level:minor host-name:"{{ host }}" system-ip:1.1.1.3 user-name:"mn2c" user-id:2227\n'

This PR adds new test cases based on the customer issue, as well as updates Cisco and Arista parsers to properly catch the differences

[srv-rr-github-token]

🎉 This PR is included in version 3.4.0 🎉

The release is available on GitHub release

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