BREAKING: Replace custom import() with normal Lua require(). (#5014)

* Use require() instead of a custom import()

* Also search relative to the current file

* Update documentation

src/controllers/plugins/LuaAPI.hpp

@@ -20,9 +20,12 @@ int c2_log(lua_State *L);
 // These ones are global
 int g_load(lua_State *L);
 int g_print(lua_State *L);
-int g_import(lua_State *L);
 // NOLINTEND(readability-identifier-naming)
 
+// This is for require() exposed as an element of package.searchers
+int searcherAbsolute(lua_State *L);
+int searcherRelative(lua_State *L);
+
 // Exposed as c2.LogLevel
 // Represents "calls" to qCDebug, qCInfo ...
 enum class LogLevel { Debug, Info, Warning, Critical };