Allowing scripts to set profiles locally

At the moment, scripts can only apply profiles globally with apply-profile. This request is for allowing scripts to apply a profile locally, either through a separate command or by passing an optional flags argument to apply-profile. (In the latter case, I'd also request #7785 or some other way of determining if this feature is available.)

Motivation: I'm the author of a plugin which applies profiles based on full pathnames (kinda like use-filedir-conf on steroids). Obviously, these profiles need to be applied on a file-by-file basis. Right now, I'm going through these profiles and applying each option individually with file-local-options/, which is far from an ideal solution. (I'm basically doing a half-assed job reimplementing m_config_set_option_cli() on my own.)

Start by tracing the existing apply-profile command and the file-local-options path, then compare them with the mentioned m_config_set_option_cli() entry point. Define how scripts apply profiles per file and how availability is detected, considering the separate-command and optional-flags alternatives; done means a script can apply a profile locally without reimplementing option handling.