Cherry-pick #26520 to 7.x: Improper casting of int64

[michalpristas]

Cherry-pick of PR #26520 to 7.13 branch. Original message:

What does this PR do?

When int64 is encountered during load agent crashes on improper casting.
Decision tree is updated so it casts correctly

Why is it important?

Bug

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.

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Pinging @elastic/agent (Team:Agent)

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Build stats

• Build Cause: Pull request #26554 opened

• Start Time: 2021-06-29T08:17:43.461+0000

• Duration: 83 min 59 sec

• Commit: 80b1454

Test stats 🧪

Test	Results
Failed	0
Passed	6916
Skipped	24
Total	6940

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Test stats 🧪

Test	Results
Failed	0
Passed	6916
Skipped	24
Total	6940