Execute a developer test for a custom tool

Requires tools:execute. Deprecated compatibility API; retained route, response shape and legacy scope. Migrate to test_http_action, actions:http:execute. Use actionId=http:<toolId>; diagnosticId=logId. New grants must be explicitly approved. No retirement date is assigned. See /api-docs/actions-api#tools-migration. Makes a real HTTP request; never retry automatically. Write-capable tests require confirmExternalEffects=true and the current configurationVersion. Obtain explicit user confirmation for this individual real HTTP request; never infer consent from management scopes or retry automatically. Missing/stale confirmation returns HTTP_TEST_CONFIRMATION_REQUIRED (403) before dispatch. Read-only tests do not require consent. This confirmation requirement also applies to deprecated Tools write tests: older clients must explicitly confirm and send configurationVersion. Explicit new Off mode returns ACTION_INACTIVE (403); historical inactive definitions without an explicit mode retain direct-test eligibility. No test endpoint for Sheets or collection actions; use Playground.