feat: update wehbook's request_timeout into resource_opts

[zhongwencool]

Fixes EMQX-9822

We hide the request_timeout in resource_option of the webhook to keep it consistent with the http request_timeout of the webhook.
From now on, when configuring a webhook through API or configuration files,
it is no longer necessary to configure the request_timeout of the resource. Only configuring the http request_timeout is sufficient, and the request_timeout in the resource will automatically be consistent with the http request_timeout.

Note: need remove resource_opts's request_timeout from dashboard webhook.

Summary

🤖 Generated by Copilot at 7d7c069

This pull request refactors and simplifies the code of the emqx_bridge application, especially the webhook bridge. It introduces a new request_timeout field for the webhook resource, deprecates an old field for the webhook bridge, and updates the version number. It also improves the readability and performance of the emqx_bridge_resource module.

PR Checklist

Please convert it to a draft if any of the following conditions are not met. Reviewers may skip over until all the items are checked:

• Added tests for the changes
• Changed lines covered in coverage report
• Change log has been added to changes/{ce,ee}/(feat|perf|fix)-<PR-id>.en.md files
• For internal contributor: there is a jira ticket to track this change
• If there should be document changes, a PR to emqx-docs.git is sent, or a jira ticket is created to follow up
• Schema changes are backward compatible

Checklist for CI (.github/workflows) changes

• If changed package build workflow, pass this action (manual trigger)
• Change log has been added to changes/ dir for user-facing artifacts update

[zmstone]

Looks good to me,
Will leave it to @thalesmg for approval.