Fix file.path field in cloudtrail data stream to use json.digestS3Object

[kaiyan-sheng]

What does this PR do?

This PR is to fix cloudtrail data stream ingest pipeline for getting file.path field. This field should from json.digestS3Object instead of json.previousDigestS3Object. Please see elastic/beats#32609 for more details.

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.

[andrewkroh]

LGTM. Needs a changelog entry.

[elasticmachine]

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• Start Time: 2022-08-22T19:24:40.082+0000

• Duration: 33 min 25 sec

Test stats 🧪

Test	Results
Failed	0
Passed	162
Skipped	2
Total	164

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[elasticmachine]

🌐 Coverage report

Name	Metrics % (covered/total)	Diff
Packages	100.0% (13/13)	💚
Files	92.857% (13/14)	👎 -4.318
Classes	92.857% (13/14)	👎 -4.318
Methods	84.232% (203/241)	👎 -5.122
Lines	95.697% (5204/5438)	👍 4.78
Conditionals	100.0% (0/0)	💚

[sayden]

LGTM