* feat: load all backends from a user-provided search path
* fix: Windows search path
* refactor: rename `ggml_backend_load_all_in_search_path` to `ggml_backend_load_all_from_path`
* refactor: rename `search_path` to `dir_path`
* fix: change `NULL` to `nullptr`
Co-authored-by: Diego Devesa <slarengh@gmail.com>
* fix: change `NULL` to `nullptr`
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Co-authored-by: Diego Devesa <slarengh@gmail.com>