Enhance cache modes in resource loading

- Unify documentation, hoping to clear misconcepctions about about propagation of the cache mode across dependant loads.
- Clarify in docs that `CACHE_MODE_REPLACE` now also works on the main resource (from #87008).
- Add two recursive modes, counterparts of `CACHE_MODE_REPLACE` and `CACHE_MODE_IGNORE`, since it seems some need them (see #59669, #82830).
- Let resources, even loaded with one of the ignore-cache modes, get a path, which is useful for tools.

core/io/resource_format_binary.h

@@ -85,6 +85,7 @@ class ResourceLoaderBinary {
 	Error error = OK;
 
 	ResourceFormatLoader::CacheMode cache_mode = ResourceFormatLoader::CACHE_MODE_REUSE;
+	ResourceFormatLoader::CacheMode cache_mode_for_external = ResourceFormatLoader::CACHE_MODE_REUSE;
 
 	friend class ResourceFormatLoaderBinary;