[eui.d.ts] Exclude all of src/test

[thompsongl]

Summary

Required for elastic/kibana#138837

The exclude glob pattern for the d.ts generator script was not accounting for nested directories with TS files. The result was that src/test/rtl/ and src/test/internal/ files and types were included in eui.d.ts (like, specifically the ones we don't want to include 🙈) and in turn included problematic types from RTL that interfere with other testing lib type definitions.

Verification:

• Checkout the v62.2.1 tag
• yarn
• Generate a new eui.d.ts
• Drop that eui.d.ts in the Kibana upgrade branch
• Type errors related to this in, say test/functional/apps/console/_autocomplete.ts should be resolved

Checklist

• Checked for breaking changes and labeled appropriately
• A changelog entry exists and is marked appropriately

[cee-chen]

Oof, awesome catch on this!!

[kibanamachine]

Preview documentation changes for this PR: https://eui.elastic.co/pr_6142/