[in_http] add options similar to add_http_headers and add_query_params found in fluentd

**Is your feature request related to a problem? Please describe.**
Not related to a problem

**Describe the solution you'd like**
The in_http plugin would be much more useful if it supported options similar to add_http_headers and add_query_params found in fluentd

add_http_headers
https://docs.fluentd.org/input/http#add_http_headers

add_query_params
https://github.com/fluent/fluentd/pull/3197

**Describe alternatives you've considered**
in_http provides a little dynamic nature on input via the URI mapping to the tag on input, but does not offer the same flexibility as found in the add_http_headers and add_query_params options