INTL-1363 : Give a better error message when something in the intl file is not a method

[alanknight-wk]

Motivation

If you declare something as a field, which people do, then the codemod crashes trying to parse it.
You're not allowed to put fields in there. Or at least we don't want to allow it. But at least make it tell you which declaration was the problem.

Changes

Add a print statement and an explicit throw rather than crashing on a cast error without telling you the problem declaration.

Release Notes

Review

See CONTRIBUTING.md for more details on review types (+1 / QA +1 / +10) and code review process.

Please review:

QA Checklist

• Tests were updated and provide good coverage of the changeset and other affected code
• Manual testing was performed if needed
  • Steps from PR author:
  • Anything falling under manual testing criteria outlined in CONTRIBUTING.md

Merge Checklist

While we perform many automated checks before auto-merging, some manual checks are needed:

• A Frontend Frameworks Design member has reviewed these changes
• There are no unaddressed comments - this check can be automated if reviewers use the "Request Changes" feature
• For release PRs - Version metadata in Rosie comment is correct

[aviary2-wf]

Security Insights

No security relevant content was detected by automated scans.

Action Items

• Review PR for security impact; comment "security review required" if needed or unsure
• Verify aviary.yaml coverage of security relevant code

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[alanknight-wk]

@Workiva/release-management-p

[rmconsole-wf]

+1 from RM