[Azure] Update null checks and if checks in the rename processor

[ishleenk17]

• Bug

What does this PR do?

This PR adds the if check for event.original and the ignore_missing check for the renaming of message to event.original
The packages where the changes are made are as below:

• azure_frontdoor

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.

Related issues

• Relates Add checks to rename processor for the message field for all Observability Integrations #7822

[elasticmachine]

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Build stats

• Start Time: 2023-09-25T05:59:43.518+0000

• Duration: 13 min 23 sec

Test stats 🧪

Test	Results
Failed	0
Passed	9
Skipped	0
Total	9

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[elasticmachine]

🌐 Coverage report

Name	Metrics % (covered/total)	Diff
Packages	100.0% (2/2)	💚
Files	100.0% (2/2)	💚
Classes	100.0% (2/2)	💚
Methods	91.667% (22/24)	👍 3.841
Lines	100.0% (290/290)	💚 3.987
Conditionals	100.0% (0/0)	💚

[kcreddy]

LGTM 👍🏼

[elasticmachine]

Package azure_frontdoor - 1.3.1 containing this change is available at https://epr.elastic.co/search?package=azure_frontdoor