cisco_{asa,ftd}: fix syslog priority handling

[efd6]

What does this PR do?

This fixes the mapping of syslog priority and its derived values and their extraction.

Checklist

• I have reviewed tips for building integrations and this pull request is aligned with them.
• I have verified that all data streams collect metrics or logs.
• I have added an entry to my package's changelog.yml file.
• I have verified that Kibana version constraints are current according to guidelines.

Author's Checklist

• This needs to be reflected into the beats ingest pipeline as well. x-filebeat/modules/cisco: fix syslog priority handling beats#32025

How to test this PR locally

Related issues

• Updates [Cisco][ASA] Syslog priority is stored in the not-ECS-compliant field syslog.facility #3507

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• Start Time: 2022-06-22T01:40:26.742+0000

• Duration: 18 min 59 sec

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Test	Results
Failed	0
Passed	48
Skipped	0
Total	48

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🌐 Coverage report

Name	Metrics % (covered/total)	Diff
Packages	100.0% (2/2)	💚
Files	100.0% (2/2)	💚 3.464
Classes	100.0% (2/2)	💚 3.464
Methods	97.143% (34/35)	👍 8.297
Lines	64.839% (2176/3356)	👎 -25.066
Conditionals	100.0% (0/0)	💚

[taylor-swanson]

LGTM

All of the syslog messages I've seen so far for ASA and FTD have not used the odd <14.2> format, just the standard format that you've changed it to here (<165>).