btif: Improve ACL connection failure reporting

This commit enhances the reporting of ACL connection failures by providing more specific error codes. Instead of always reporting `BT_STATUS_FAIL` when a link up fails, we now map the underlying HCI error code to a more informative `bt_status_t` value. This allows higher-level components to better understand the cause of the connection failure. E.g., Floss metrics system which tracks connection failure reasons.

Bug: 353527430
Test: mmm packages/modules/Bluetooth
Test: manually verified new error code are used
Flag: EXEMPT, error code refactoring, no logic change
Change-Id: Icafe9fd5032f732477beb9e680dc6b69cb0035a1