feat: support tcp_check_http_method

[mzz2017]

Motivation

tcp_check_http_method is the HTTP request method to tcp_check_url. Use 'CONNECT' by default because some server implementations bypass accounting for this kind of traffic.

Usage

global {
  #...

  # The HTTP request method to `tcp_check_url`. Use 'CONNECT' by default because some server implementations bypass accounting for this kind of traffic.
  tcp_check_http_method: CONNECT
}