* admin: Refactor /load endpoint out of caddy package
This eliminates the caddy package's dependency on the caddyconfig
package, which helps prevent import cycles.
* v2: adapter: register config adapters as Caddy modules
* v2: adapter: simplify adapter registration as adapters and modules
* v2: adapter: let RegisterAdapter be in charge of registering adapters as modules
* v2: adapter: remove underscrores placeholders
* v2: adapter: explicitly ignore the error of writing response of writing warnings back to client
* Implicitly wrap config adapters as modules
Co-authored-by: Matthew Holt <mholt@users.noreply.github.com>