Add geocoding debug logging

It seems that in the WP_Job_Manager_Geocode:: get_location_data() when there is an error, the method does return a `WP_Error` after throwing an Exception -- but from what I can find, that isn't actually used, caught or dealt with anywhere.

So what i'm thinking is maybe we can add a filter that a user can enable when they are having issues, that would essentially write to the `error_log` instead of just returning a `WP_Error` that is never dealt with.

Thoughts? I can submit a PR for this but wanted to start a discussion on it to see others thoughts

@jom

Start by tracing WP_Job_Manager_Geocode::get_location_data() and how its WP_Error and Exception paths are handled. Review the proposed filter and error_log behavior, then clarify the expected opt-in logging scope and verify that geocoding errors are observable without changing normal error handling.

Written by the indexing model from the issue text.