Make healthcheck_path optional on services

Previously services had to be configured with an ALB path and a healthcheck path; for example:

module "ingestor" {
    source           = "./terraform-modules/services"
    path_pattern     = "/ingestor/*"
    healthcheck_path = "/ingestor/management/healthcheck/"
}

The module now tries to guess a better default healthcheck path, by appending /management/healthcheck to the path pattern. So this is equivalent to the code above:

module "ingestor" {
    source           = "./terraform-modules/services"
    path_pattern     = "/ingestor/*"
}