http: migrate aws_lambda/admission_control/... to exception free

[wbpcode]

Commit Message: http: migrate aws_lambda/admission_control/... to exception free
Additional Description:
Migrate exceptions of these filters to absl::Status and absl::StatusOr.

NOTE: This is AI assisted. But I reviewed all the changes and tests, and also did some manually update.

Risk Level: low.
Testing: unit/integration.
Docs Changes: n/a.
Release Notes: n/a.
Platform Specific Features: n/a.

[Copilot]

Pull request overview

This PR continues Envoy’s exception-free migration for HTTP filter factory creation by removing exception-throwing wrappers and directly returning absl::StatusOr<Http::FilterFactoryCb> results from helper factory builders.

Changes:

• aws_request_signing: return the helper StatusOr directly instead of translating failures into EnvoyException.
• aws_lambda: return the helper StatusOr directly instead of throwing on non-OK status.
• admission_control: return StatusOr directly instead of THROW_IF_NOT_OK_REF(...) + .value() extraction.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
source/extensions/filters/http/aws_request_signing/config.cc	Removes exception-throwing wrapper and returns helper StatusOr directly for exception-free factory creation.
source/extensions/filters/http/aws_lambda/config.cc	Removes exception-throwing wrapper and returns helper StatusOr directly for exception-free factory creation.
source/extensions/filters/http/admission_control/config.cc	Replaces throw-on-error extraction with direct StatusOr return to align with exception-free behavior.