[AWS CloudTrail] use json.digestS3Object for file.path

[kaiyan-sheng]

What does this PR do?

This PR is to fix a bug in CloudTrail fileset ingest pipeline: instead of json.previousDigestS3Object, we should use json.digestS3Object for file.path.

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files
• I have added tests that prove my fix is effective or that my feature works
• I have added an entry in CHANGELOG.next.asciidoc or CHANGELOG-developer.next.asciidoc.

closes #32609

[mergify]

This pull request does not have a backport label.
If this is a bug or security fix, could you label this PR @kaiyan-sheng? 🙏.
For such, you'll need to label your PR with:

• The upcoming major version of the Elastic Stack
• The upcoming minor version of the Elastic Stack (if you're not pushing a breaking change)

To fixup this pull request, you need to add the backport labels for the needed
branches, such as:

• backport-v8./d.0 is the label to automatically backport to the 8./d branch. /d is the digit

[elasticmachine]

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• Start Time: 2022-08-22T21:00:51.720+0000

• Duration: 134 min 11 sec

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Test	Results
Failed	0
Passed	4399
Skipped	338
Total	4737

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[tommyers-elastic]

is there an issue for this?

[kaiyan-sheng]

@tommyers-elastic Yep I just linked the issue.