ti_misp: Fix the processing of ISO8601 dates

[chemamartinez]

Proposed commit message

The current implementation assumes that first_seen and last_seen attributes are in UNIX epoch format, microseconds granularity.

Now we have seen examples of dates in ISO8601 format, as the MISP documentation states. Leading to the following error:

in the ingest pipeline on the script-default-decayed_at : Processor script with tag script-default-decayed_at 
in pipeline logs-ti_misp.threat_attributes-1.35.2 failed with message: For input string: "2024-10-06T16:48:04.000000+00:00", 
Processor date with tag date_attribute_first_seen in pipeline logs-ti_misp.threat_attributes-1.35.2 failed with message: For input string: "2024-05-11T12:54:49.000000+00", 
Processor date with tag date_attribute_last_seen in pipeline logs-ti_misp.threat_attributes-1.35.2 failed with message: For input string: "2024-10-06T16:48:04.000000+00"

Changes introduced at this PR make sure that the pipeline is able to process both formats.

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.
• I have verified that any added dashboard complies with Kibana's Dashboard good practices

[elasticmachine]

Pinging @elastic/security-service-integrations (Team:Security-Service Integrations)

[elastic-vault-github-plugin-prod]

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[elasticmachine]

💚 Build Succeeded

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• Commit: 4ab7a7e

cc @chemamartinez

[elastic-sonarqube]

Quality Gate passed

Issues
0 New issues
0 Fixed issues
0 Accepted issues

Measures
0 Security Hotspots
86.7% Coverage on New Code
0.0% Duplication on New Code

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[efd6]

Remember to convert the commit message from md, git history is not markdown.

[elastic-vault-github-plugin-prod]

Package ti_misp - 1.35.6 containing this change is available at https://epr.elastic.co/search?package=ti_misp