fix(xecguard): use StandardLoggingGuardrailInformation in logging hook

[yucheng-berri]

Closes LIT-4335.

XecGuard's async_logging_hook wrote a bare dict to standard_logging_object['guardrail_information'] instead of a properly typed StandardLoggingGuardrailInformation wrapped in a list. This broke downstream loggers that expect List[StandardLoggingGuardrailInformation].

Changes:

• Construct a proper StandardLoggingGuardrailInformation TypedDict
• Wrap in a list / append to existing list (consistent with the base class method)
• Update test assertions to validate list-of-dict shape

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

[yucheng-berri]

Closed and recreated as #32911 on a litellm_ prefixed branch with corrected commit authorship

[codspeed-hq]

Merging this PR will not alter performance

✅ 31 untouched benchmarks

---

_{Comparing fix/lit-4335-xecguard-guardrail-info-type (a9895f6) with litellm_internal_staging (a4199d3)}