[crowdstrike] Fix multi-line string handling for config variable

[andrewkroh]

What does this PR do?

The default value for fdr_parsing_script is a multline string. When the handlebar
template was evaluated this created invalid YAML. By changing the variable type to
'yaml' Kibana produces config that is valid. It looks like

sqs.notification_parsing_script.source: >-
      function parse(n) { var m = JSON.parse(n); var evts = []; var files =
      m.files; ...

I cannot find any documentation for the 'yaml' variable type so I hoping this is how it was
expected to be used.

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

• Closes [crowdstrike] 'Is FDR queue' option not being honored #2646

Screenshots

Before:

After:

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Pinging @elastic/security-external-integrations (Team:Security-External Integrations)

[elasticmachine]

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• Start Time: 2022-02-15T23:37:29.968+0000

• Duration: 21 min 2 sec

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Test	Results
Failed	0
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Total	13

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[efd6]

LGTM mod knowing that this is how it's supposed to be used.