updater: Remove some obsoleted functions for file-based OTA.

This CL removes the updater support for delete(), symlink(), rename(),
set_metadata() and set_metadata_recursive(). Such functions have been
removed from the generation script in commit
f388104eaacd05cfa075d6478369e1d0df5ddbf3 (platform/build).

Note: This CL also removes delete_recursive() which seems to have never
been supported in generation script.

Bug: 35853185
Test: recovery_component_test passes.
Change-Id: I51e1ec946fa73761118fa1eaa082423df6d588e9