HTTP Input GET method should return "alive" or similar

[agup006]

When using Fluent Bit in_http plugin the only approved method is a POST. However when using Fluent Bit with an ingress on K8s across major Cloud Providers the default health checks use a GET on top of the Kubernetes service which can cause problems if you want to expose Fluent Bit's in_http plugin

Ideally, Fluent Bit can have the following: A new parameter allow_healthcheck which gives the ability to a user to issue a GET request on the same port and get a 200 response. The reason to have a new parameter is that if adding to exsiting in_http it could break logic where a GET fails today

[edsiper]

Implementation here: #10020

regarding the extra configuration option, I am not sure why it might be needed...